I like the idea of $350 sell out price but I think it does not have to be RTR and you can set price for each of the significant components so you don't have to part with the whole car if someone claims it. Like say you can claim the motor for $50, the chassis for 200, the esc for $65, servo for $65, so on and so fourth. Also make certain part of the car not claimable like the body etc. Store also need a ready package that retails for cheaper than the price you set so anyone can jump in and be competitive. I would suggest cheap spec motor and fixed gearing ratio. I would also set a max number of time you can claim someone else's car or parts per season so no one is abusing it. Also I think you should not be able to buy other's car or parts unless you already have a setup to race with.

I think this have been done in Finland for weekend real car racing series and works quite well.