Formula-based pricing

Price a stage from a driver like construction cost: store the cost as a hidden reference, then add a formula revenue item that calculates from it and recalculates live.

A flat fixed fee is fine when the number is, well, fixed. But a lot of architecture pricing is a percentage of something — most often a percentage of construction cost. When the construction cost estimate changes, you want the fee to change with it, automatically. That's formula-based pricing.

We'll price the Concept Design stage of Riverside Apartments as ten percent of construction cost.

The idea: store the driver, then calculate from it

A formula needs something to reference. So it's two items working together:

A driver — the construction cost — stored as a revenue item so the rest of the model can point at it. You hide it, because it drives the fee but isn't itself money you earn.
A formula item — your fee — written as an expression that references the driver: {revenue.construction_cost} * 0.1.

Once they're linked, the fee isn't a number you maintain — it's a calculation. Change the driver and every fee built on it moves.

Build it

1
Select the Concept Design stage and open its revenue.
2
Add a Fixed Amount item, name it Construction Cost, and set it to two million dollars.
3
Hide it — it drives the fee, but it isn't revenue you bill.
4
Add a Formula item and enter {revenue.construction_cost} * 0.1.

Where the reference name comes from

Monument turns each item's name into a reference slug — "Construction Cost" becomes construction_cost, in the revenue namespace. So your formula reads {revenue.construction_cost}. The references list in the formula editor shows you exactly what's available to point at.

Watch it recalculate

This is the payoff. The fee is now live: edit the Construction Cost to three million and the calculated revenue jumps to three hundred thousand; drop it to one million and the fee falls to one hundred thousand — no re-typing, no stale numbers.

That's the difference between a price you wrote down and a pricing model. The model stays correct as the project's inputs move.

Reuse it everywhere

Because this is just items and a formula, you can save the whole stage as a template and start every future project with your standard construction-cost pricing already wired up.

Gotchas

Formula shows an error or zero. Check the reference name matches the driver's slug exactly — rename the driver and the slug changes with it.
The fee double-counts. If both the driver and an old calculated item are visible, they both add to the total. The driver should be hidden; only the formula item should count.
Percentages are decimals. Ten percent is * 0.1, not * 10.

Where this fits next

You've got a pricing model worth keeping. Next, capture it so you don't rebuild it each time: pricing templates.