"1) a gaming PC is substantially more expensive than a console"
False. You can buy a new computer, good enough to play most games out there, including monitor for $300-$400, or a similar laptop for $400. Xbox 360 and PS3 were more expensive than this when they came out. Also, games for consoles are not less than $50 for the most part, while most PC games are normally at least $10 cheaper. And in the case of the 360, you even have to pay an extra $50/year to play online. Is it really cheaper?
"2) you frequently have driver and other compatibility problems"
It might be true, although as a heavy gamer myself, I don't remember when was the last time I experienced this. Think it was some 7 or so years ago.
"3) a number of PC games are launched in a rather buggy state"
True for the vanilla CD/DVD version you take out of the box, but chances are by the time you install the game, there's already a patch auto-updated by the game.
"4) the overall performance level of consoles has improved a lot in the latest generation"
Indeed, which is about the performance of a 2-3 year old video card.
Truth is, the real deterrent for developers is piracy. Yes you can pirate console games, but the issue is much more rampant in the PC world. Seems like only the mostly online games like MMOs (where you have to pay a monthly fee, regardless if you have a pirated copy of the game or not) and the casual games (where mom and grandma don't even know that games can be pirated) are financially successful for PCs.