Every idle game eventually feels like it stops. You buy an upgrade, the counter ticks a little faster, and then the next one costs so much that nothing happens for ten minutes. That feeling is not a bug and it is not bad balancing. It is a deliberate geometric cost curve, and once you can read it you stop guessing at purchases.
The multiplier that runs the genre
Most incremental games price a building using a fixed ratio rather than a fixed increase. Buy one, and the next one costs the base price times a constant. The convention the genre inherited from Cookie Clicker is 1.15: each additional copy of a building costs 15% more than the last one.
The formula for the n-th copy is:
cost(n) = base_cost × 1.15^(n-1)That exponent is what makes the wall. A few checkpoints, assuming a base cost of 100:
| Copies owned | Cost of next | Total spent so far |
|---|---|---|
| 0 | 100 | 0 |
| 10 | 405 | 2,030 |
| 25 | 3,292 | 21,800 |
| 50 | 108,366 | 737,000 |
| 75 | 3,566,000 | 24,300,000 |
Your production, meanwhile, grows linearly with copies owned: 50 copies produce exactly 50 times one copy. Linear output against exponential price is why the tenth copy of something feels free and the fiftieth feels impossible.
Payback time is the only number that matters
Because production is linear and cost is exponential, comparing raw prices across different buildings is useless. The usable metric is payback time: how many seconds of that building’s own output it takes to repay its price.
payback_seconds = cost_of_next_copy / production_per_second_of_one_copyRank every available purchase by that number and buy the lowest one. That single habit is worth more than any upgrade order guide, because it automatically adapts as your economy shifts. A cheap early building with a 40-second payback is a better buy than a flashy new tier with a 900-second payback, no matter how impressive the new tier’s icon looks.
In Idle Money Factory this is very visible, because the game splits progress across production lines, machine enhancements, and unlocking new factory sections. The new section always looks like the exciting purchase. Run the payback number and it frequently is not — an enhancement on a line you already own often repays itself in a fraction of the time.
Why the curve breaks and what resets it
A pure 1.15 curve would stall forever. Designers break it with three tools:
- Multiplier upgrades. These do not add copies, they multiply the output of copies you already own. Against a linear production term, a 2x multiplier is equivalent to instantly doubling your building count — which on the cost curve would have taken roughly
log(2)/log(1.15) ≈ 5more copies at that tier. That is why multipliers are almost always the correct purchase when their payback time is anywhere near competitive. - New tiers. A fresh building type resets the exponent to n=1, which is why unlocking a tier feels so good and then decays within twenty purchases.
- Prestige. A full reset that trades your current total for a permanent global multiplier, deliberately re-flattening the curve.
Clicker Hero shows the tier version clearly: gold buys heroes, heroes deal damage automatically, and tougher monsters drop more gold. The loop only keeps moving because new heroes keep resetting the exponent while your old heroes keep their levels.
Reading a curve you cannot see
Most browser idle games never show you the ratio. You can estimate it in about thirty seconds:
- Note the current price of one building.
- Buy one copy.
- Note the new price.
- Divide the new price by the old one.
If you get roughly 1.07–1.10, the game is generous and hoarding that building is correct. Around 1.15 is standard. Anything over 1.25 means that building is designed as a short burst — buy a handful and move on, because the tenth copy will cost nearly ten times the first.
Try it in Tiny Farm, where crops, animals, and farm unlocks are all priced on separate curves. The crops usually sit on a gentle ratio and reward stacking; the farm unlocks sit on a steep one and are meant to be milestones, not a grind target.
The practical loop
Check the ratio, compute payback time for every option on screen, buy the lowest, repeat. When the lowest payback time on the board climbs past what you are willing to sit through, that is the game telling you the current run is finished and it is time to look at a reset mechanic instead of another purchase.
Want more of the same loop? The full clicker category is built around games where this math actually applies.
