I dunno, after you've already got the tools and whatnot, I'm not so sure that buying a guitar is cheaper than making one. When you build your "ultimate" guitar, you want it a specific way. If you were to order something custom from PRS (not sure if you can, but it's a nice example), i'm imagining the costs would be nuts. Their "high" end guitars cost an arm and a leg.
If you are planning on this being the only guitar you build, it's definitely going to cost you an insane amount of money. But if you're lookin at this as something you want to continue with, building guitars that suit your fancy shouldn't cost you more than a decent guitar in the store. I actually started building guitars because i couldn't afford to buy the guitar i wanted ($4200 US) and after building it and buying every single power tool, hand tool and supply that i wanted and needed, i still haven't hit that 4200 mark.
Buliding guitars is not a cheap hobby, but the rewards are priceless.