eBay =)
I got mine shipped to my door for $355. brand new.
My friend paid slightly more for his ($370) but his is the newer "2003" model, mine was an older model, although never used.
Remember that there's a lot of little extras no matter what one you get. Figure that you'll have to spend another $200 for the required gear, batteries, chargers, fail safe, new shock towers, various fluids..
I say Shock Towers because the Storm RTR's towers are severly weak. They will bend on you just from driving the thing. Replacements aren't very expensive.
Overall it's pretty tough to beat the Storm RTR in terms of value!