Then perhaps the answer is raise fees for racing to $20 for everyone?
If you have a transponder of your own, you are just saving time and hassle with swapping out rental units.

But if the track is incurring costs because racers are leaving at the end of the day with transponders, that's another issue. Then it is the users of rental units that need to foot the expense.

I suspect it is a good time for someone to do another bulk purchase of AMB's and start selling them, because the demand is going to increase.