I worked for a company that would do this exactly, with an additional variable. The sales folks' bonuses were based on the original estimate, not any overruns.

I worked for a company that would do this exactly, with an additional variable. The sales folks' bonuses were based on the original estimate, not any overruns. So they'd promise the customer a certain feature set then, write up the minimum feasible estimate, collect their bonuses, then blame engineering for the extra cost, feature creep, etc... when it was all by design.