There are cheaper solutions out there. I-Lap is one, and their transponder cost about $25. Is it as good as RC4? You have to put the I-Lap transponder high and closer to the clear windshield area in order to get read.

RC racing by no mean is a low cost hobby. To bash around will be a lot cheaper, and you don't need a transponder.

As I always tell the new comers to get on rctech to buy an used RC4 for $75-$85. It's basically a free rental. That thing doesn't break. Just sell it when you are done or out of the hobby. Help yourself by buying one for each class you race. Moving transponder from one car to another is pain in the bud. Again, it's free rental!!!!