The initial investment might be higher than consoles*, but most folks need a PC anyway. If you build your own PC (or buy a custom pre-built, if building isn't your thing) and then throw in a $150-200 GPU every generation or so, you gain the benefits of a PC with the affordability of a console.
*Assuming we're buying well into the console's life. $500/600 PlayStation 3 and $400 Xbox 360 at launch isn't much cheaper than a decent PC.
Edit- Not that consoles aren't a good option, just saying that PC doesn't have to be as expensive as folks make it out to be.
