Sure, you have to do a lot more QA and support than on consoles. And there will be some PC specific development, both for the engine and for amenities that PC p

Sure, you have to do a lot more QA and support than on consoles. And there will be some PC specific development, both for the engine and for amenities that PC players expect like keyboard+mouse support, graphics options, etc. But the biggest costs in AAA gamedev aren't going to be platform specific. The assets (textures, models, animations, sound fx, music, level designs) should just port over. Likewise most marketing will be platform agnostic; you don't have to triple your marketing budget when going from one platform to three. And art + marketing is probably like 70%-80% of the budget. The marginal profitability of a PC port should thus be extremely high. (Which is why pretty much every AAA game will launch on the PC too, not just on the consoles. If the PC really was a marginal and expensive platform, they wouldn't bother).