depends what class you want to run. If your going to run truck go on ebay and buy an RC10gt. The new GT2 has a different gear ratio in the tranny, and can be difficult to get the right ratio with foam tires. I haven't seen a GT2 that handled right yet. Usually you can find a good GT on ebay for around $150. Till you get tools, starter box, etc. etc. $400-$500.
If you want to run sprint car, latemodel, or edm, its more then twice that. For a custom works sprint car your looking around $475 for just the roller. A bms sprint is $525. Late models and edm's use the same chassis, from custom works they are around $440, from BMS they are $510. Then you will need a radio, motor, etc.
you can go here and get more of an idea:http://www.newvillercspeedway.com
what does it cost to get into something like this....i know how fast do you want to go.
how about how much for getting started as a hobby and how much to compete with the big dogs.