Personally, I feel like there's more nuance to it than that, but it would basically become incalculable. There's the whole deal with how streamers should be able to carry games and whatever they're playing not being super important, that it's their personality that makes them money. Now we know Dave has the charisma of a blobfish and he goes on about new releases with fun and interesting gameplay being the reason people donate, but I think the same standards should apply to him.
So I feel like not only does he have to make the $65 (let's be generous and give him $5 for sales tax) the game cost, but he has to make money on top of that to actually gain. As much as he memes about playing games for fun and enjoying them, he is still doing this trying to generate income and, on a new release, breaking even isn't breaking even. I say this because he could theoretically be playing any other game he already owns and it'd basically be 100% profit.
So just making back the cost of the game doesn't cover it, imo. One thing that's incalculable is discerning which donations are there because people are interested in him watching that (for whatever reason -- it's irrelevant) or were not interested in watching something else. I imagine he'll actually see a bump in donos today because, as much fun as it is to watch him raging at MK, he doesn't have enough downtime to sperg out at bait messages like he does during games like Minecraft and Blackout, deincentivising interaction during those streams.
So you can't accurately place those numbers, but I want to say maybe 25-30% is due to game choice?
And then you have the fact that a lot of games are stretched out over the course of multiple streams, so it's even harder to track. Now, I still don't think that he's ever lost money like that on a game before, but I'm just tossing in my two cents that I think it goes beyond just making back the cost of the game since streaming literally anything else would be pure profit.
