Obsidian was promised a bonus from Bethesda alongside straight payment on Fallout: New Vegas if it had hit an 85 on MetaCrtiic.
The info was mentioned in a tweet by studio co-founder Chris Avellone when asked a question by a fan following recent lay-offs at the company.
"FNV was a straight payment, no royalties, only a bonus if we got an 85+ on Metacritic, which we didn't," said Avellone.
Fallout: New Vegas launched in October 2010.
It was reported yesterday that Obsidian had been hit with up to 30 layoffs, linked to a next-gen Xbox title codenamed North Carolina that would have been published by Microsoft.
The workforce reduction hasn't been confirmed yet.