The new CEN Matrix R2 RTR goes for around $250-$300. It's a good buggy to take a look at. If you would want something better suited for racing, the R2 FRE will be coming out shortly, and you can pre-order now for a discounted price! PM me for more info.
If you don't want to buy new, a used buggy would save you money. You can find nearly anything on ebay for a good price.