My source is first and second hand reports from management of game companies having worked in the industry for decades. But, they don’t make numbers like that public.
The best public report I can find is https://www.sciencedirect.com/science/article/abs/pii/S18759... which shows a median difference 20% of revenue for games where Denuvo is cracked “quickly” but also no significant difference if Denuvo survives for at least 3 months.
What I’ve observed from internal reports from multiple companies is that, if you don’t assume an outlier blockbuster game, major game studios’ normal plan is to target a 10% annual profit margin with an expected variance of +/-20% each year.
So, assuming you have a solidly on-target game, DRM not just being there, but surviving at least a couple months is the difference between “10% profit moving the whole company forward on schedule” vs “10% loss dragging the whole company down” or “30% profit, great success, bonuses and hiring increases” depending on the situation.
Outside of games, I have seen many personnel reports on Hacker News over the years from small-time ISVs that they find it exhausting they need to regularly ship BS “My Software version N+1” just as an excuse to update their DRM. But, every time they do, sales go back up. And, the day the new crack appears on Pirate Bay, sales drop back down. Over and over forever. Thus why we can’t just buy desktop software anymore. Web apps are primarily DRM and incidentally convenient in other ways.