The cost of building an E-Revo all depends on how you want to do it! You can use the kits available to modify an existing chassis or what I did was went the gorillamaxx route. Gorillamaxx is with out a doubt the more expensive route but I'm extremely happy with it.
Used gorillamaxx rolling chassis on ebay(came with radio and steering servo as well) - $300
Novak HV 4.5 motor +esc on ebay - $230 (not the best choice but I didn't do any research, your on the right track!)
Tires and Wheels (Traxxas talons mounted on traxxas gemini rims) - $80
2 fast chargers $70
2 4500 mAh packs from ebay - $60
2 4200mAh 7 cell venom packs - $120
body and paint - $45
battery connectors - $15
Now upgrading to a 5mm shaft in my motor after snapping the 3.2mm, gorillamaxx single speed tranny from e-bay to allow a revo spec slipper(e-maxx slippers suck!!!) another $150
Altogether it can be very expensive! How dedicated are you? As I said I'm extremely happy with my E-revo, I have pulled off a full back flip just from punching it from a stop and I don't have to tune it for the weather! I wish I had done some research on here b4 I built mine but I did it all on a whim one night and went crazy on ebay. The gorilla chassis is expensive but it's awesome. The Novak motors and esc aren't the best choice at all. If your not in a hurry I recomend waiting till some people get the mmm in their hands and see if they're happy with them, otherwise go with the faigo or neu or something along those lines but I recomend staying away from Novak. Altogether right now I have about $1100 wrapped up into mine, compared to the other $1400 total I have into a T-maxx 2.5R, Revo 3.3, and brushless RC18T combined! No one ever said R/C was cheap! If you wanna play you gotta pay and if you wanna run with the big dogs you hadn't better be affraid of melting ur credit card, LOL!
I have plenty of pics on my myspace profile
www.myspace.com/jt13031