A booking app can be small enough to build and still have several running costs: the platform, a domain, a connected service and the time someone spends maintaining it. Before you choose the first version, put those assumptions in one place.
This guide belongs in Part 1 of the five-part Overskill build guide: choose a problem worth solving. It helps you estimate the recurring cost of one workflow and see which amounts still need checking. You will leave with three monthly scenarios, a separate setup amount and a downloadable record of your assumptions.
Overskill turns written instructions into an app you can review and refine. Use this cost plan to decide what you can operate before writing those instructions. The calculator below uses your inputs. It does not read your account, predict AI credit use or supply current vendor prices.
Start with one workflow
Describe the app in one sentence, such as “Clients submit a request and staff reply in a shared portal.” Include only the services needed for that first journey. A future video library or SMS reminder feature belongs in a later version unless you intend to operate it now.
For each cost, record its name, billing period or usage unit, price source and date checked. The Price source or assumption field accepts a short note. It does not fetch or verify the destination you type.
Check current Overskill pricing for the plan and credit terms that apply to your account. Credit use varies with the AI work and follow-up changes; counting prompts does not establish a bill. Check connected services separately. This guide includes no real plan prices or preset credit conversion.
Compare your scenarios
Build your cost ledger
Start blank or load the fictional example. Add a fixed row for a service's base fee and a metered row for its usage. Enter 0 only when zero is a known assumption; exclude a row if it is outside this plan.
Monthly equivalents, with gaps visible
Yearly fixed amounts are spread across twelve months for comparison. This does not change when the invoice is due. Usage charges are prorated, with each row rounded to cents before the total.
Scroll horizontally to compare all cost columns.
| Cost row | Low / month | Base / month | High / month | Billing note |
|---|
One-time work
Fixed annual invoices
The JSON includes your input rows, missing amounts, scenario results and calculation limits. Show the snapshot to review it, or copy it if your browser does not save downloads. Save the text in a file you control. This page does not import JSON or save a plan online.
Show the JSON snapshot to review or copy your current plan.
Start with your own blank ledger, or choose Load fictional example to inspect the method. The six initial rows cover a platform, a domain, a service base fee, metered usage, maintenance and setup. You can rename them, remove them or add fixed and metered rows, up to twenty in total.
A fixed row has an amount and one billing period: monthly, yearly or once. A metered row has a rate per one or one thousand units, an included monthly quantity, and low, base and high usage. Keep the same unit throughout a row. A rate per hour needs quantities in hours; a rate per thousand calls needs quantities in calls.
The three scenarios apply your entered quantities. They are not predictions. Use low ≤ base ≤ high when all three quantities are known. If you do not know a required amount, leave it blank. Enter zero only when zero is the assumption you intend to make.
Reproduce the fictional example
The example is a teaching ledger for a small app. Every price is invented, including the platform amount. None is an Overskill quote or a connected-service offer.
Scroll horizontally to compare all columns.
| Cost | Entered assumption | Monthly comparison |
|---|---|---|
| Fictional platform | $120 billed monthly | $120.00 |
| Fictional domain | $24 billed yearly | $2.00 |
| Fictional service base fee | $10 billed monthly | $10.00 |
| Fictional metered service | $2 per 1,000 units; 100 units included monthly | Depends on usage |
| Fictional maintenance | $30 per hour; 2 hours in each scenario | $60.00 |
| Fictional setup | $200 once | Kept outside recurring totals |
Fixed monthly equivalents plus maintenance contribute $192. The usage row charges only for the quantity above the included 100 units:
Scroll horizontally to compare all columns.
| Scenario | Monthly units | Billable units | Usage charge | Modeled monthly total |
|---|---|---|---|---|
| Low | 300 | 200 | 200 × $2 ÷ 1,000 = $0.40 | $192.40 |
| Base | 1,000 | 900 | 900 × $2 ÷ 1,000 = $1.80 | $193.80 |
| High | 4,000 | 3,900 | 3,900 × $2 ÷ 1,000 = $7.80 | $199.80 |
The $200 setup amount stays separate. The domain still has a $24 annual invoice: displaying a $2 monthly equivalent does not move its payment date. This calculator does not assemble a first-month invoice.
Try three changes before replacing the example:
- Change high usage from 4,000 to 8,000. High becomes $207.80; low and base stay $192.40 and $193.80.
- Clear the metered-service rate. Each scenario shows a $192.00 known subtotal and names the unpriced row. Usage has not become free.
- Enter zero for that rate. All three modeled totals become $192.00 because you have now supplied an explicit zero-price assumption.
Download the fictional example JSON to inspect the input rows and results together. Open the editable cost worksheet for a manual version of the same exercise.
Keep gaps and payment timing visible
The calculator adds the known rows even when another row is unknown or invalid. Known subtotal is the priced portion; Modeled total means every included row in that scope has a known input. Neither label guarantees that you remembered every cost.
Blank setup affects the one-time section without hiding a complete recurring comparison. A blank yearly amount stays unpriced and is absent from the list of known annual invoices. Excluding a row leaves it out of the calculation while keeping its values available if you include it again. All rows excluded means no included costs, not a confirmed zero bill.
Annual fixed amounts are divided by twelve, and each row is rounded to cents before addition. Rounding halfway goes up. For example, a fictional $0.06 annual amount contributes $0.01 to a displayed monthly equivalent; twelve displayed cents would not equal that six-cent invoice. Keep the original annual amount for payment planning.
Know when this method does not fit
Metered charges here use a linear calculation:
max(monthly quantity − included quantity, 0) × rate ÷ unit size
The tool does not infer tiers, minimum charges, whole-block purchases, carryover, tax, currency conversion or payment-processing fees. It cannot turn a vendor's credit bundle into a trustworthy per-prompt price. Use the service's actual billing method when those details matter. A verified fixed service base fee can be a separate row; an unknown one should remain blank.
All amounts use USD. Inputs accept ordinary nonnegative decimals up to four decimal places and at most 1,000,000,000. Enter 1000, without a currency symbol or comma. Invalid inputs remain visible instead of silently becoming zero.
Keep a record and choose the next step
Choose Download this cost plan after changing your own inputs. The JSON contains the rows, source notes, unknowns, exclusions, results and model limits. Show plan JSON gives you a visible snapshot; Copy plan lets you keep that text when a browser does not save the download. If clipboard access is unavailable, select the JSON and copy it with your device's usual controls. Save it in a text file somewhere you control.
Editing a field clears the displayed snapshot, so show or download a new one after a change. The tool has no import feature: an exported file is a record, not a plan you can reopen in this page. Clearing the form, leaving or reloading starts again with blank assumptions.
Use the result to write down three decisions: the workflow you will build first, the costs you have checked, and the unknowns that need an owner. If the scope is too uncertain, reduce it before building. Assign maintenance to a person; a small hourly estimate is useful only if someone will do the work.
Continue to Part 2: plan your app's workflow, choose a relevant example, then make your app brief. Describe the smallest useful journey and the services it depends on. Keep account details and credentials out of the brief. Start build carries that brief into Overskill's normal account and build flow; access, credits and setup requirements still apply. The cost plan is not automatically attached or imported.
When someone else will operate the app, use the MCP handoff worksheet to agree who owns the running costs and support. Keep the estimate beside the eventual invoices and revise your assumptions from actual use.