The Witcher 3 priced its whole economy with polynomial least squares curves

Speaking at GDC Europe, The Witcher 3 senior gameplay designer Matthew Steinke revealed that one of the game's core systems barely existed months before release: the economy, crafting and inventory were 'fragmented and incomplete' to the point that 'there was no time left in the project to accomplish everything by the deadline.'

Steinke started from a state diagram of the 'cycle of spending' — loot funds better gear, better gear unlocks tougher fights and more loot. Hand-guessing prices for herbs, junk and books failed fast, so he built a formula scoring each item's combat attributes into an overall rating, organized items into nine generalized categories, and used polynomial least squares to chart each category's price progression against quality.

The first curves were wrong for the game's grounded tone: at the low end, a small quality gain spiked the price. He re-tuned the curves to grow slowly until the endgame, so the final relic sword felt like a real fortune. Then came the practical trick: by pre-calculating the coefficients and storing them in tables, prices could be procedurally generated at run-time — an infinite set of points fitting the curve exactly, with hardcoded values removed and a whole class of bugs eliminated.

Chart each item category's price progression with polynomial least squares, then store the coefficients in tables so prices generate themselves at run-time.

There was no time left to hand-price thousands of items across a huge open world.

Guessed prices produced incoherent relationships between item categories.

Curves expressed the design intent directly: early-game scarcity, late-game wealth.

Runtime generation meant new or modded items priced themselves consistently.

When you cannot hand-tune a system in time, model it as a curve and ship the coefficients — the math generates unlimited content and deletes the hardcoded values that cause bugs.

The Witcher 3 shipped in May 2015 with the curve-driven economy tying together its crafting, inventory and loot systems, and Steinke's GDC Europe talk became the public account of how the deadline panic produced the method.