A LOT of that budget is going into advertising. I mean they have building sizes adverts all over major cities in the US and Europe (maybe more than I know of).
As for a PC version, I strongly suspect we will get one, but we won't get one until they release an enhanced edition for the next-gen consoles. Makes sense really.
Also it seems like they have a lot riding on GTA Online, so they will want it on as many systems as possible.
I preordered for a console because I love the series too much to wait, this is the one and only franchise I would ever buy twice like that.