"Also if you don't already have a good monitor, that's even more of an investment"
Just like an xbox needs a TV to be used and TVs, at least good ones, are far more expensive than monitors.
" you forget the a console gamer can buy used games at a store"
for less than 15% off the price of a new version and your trade ins will net you a pittance. On the PC I could preorder Borderlands 2 for $35 with a season pass and a free copy of XCOM: Enemy Unknown, a then $50 title.
I play around 15-20 games a year and I spend less than $100 on the lot of them. XBox live alone nearly meets that price line and the $10 console markup rate on most games along with the lack of giant sales means that even if you buy 5-7 games a year at only +$20 each over the PC counterpart you have earned enough every 2 years to buy a new graphics card. Also I use my old graphics cards as physx cards and I am able to run most new AAA games at ultra with a 650Ti Boost ($150 at retail). Add to that I can use my PC for general use you save far more money gaming on a PC.
Furthermore, to suggest that a console owner saves money based on a 1:1 comparison between the cost of a console and the cost of a PC you also have to assume that the console owner doesn't own a PC. Really what needs to be compared is the marginal cost between a standard computer and a gaming rig which is less than $400 even if you are being generous.
The console being more cost effective is a myth. The real draw to a console is that it is an out of the box solution, no messing around with third party apps an installers, and much more effective local multiplayer.