From what I have seen on Ebay and sale or clearance items from online hobby shops, some Scalextric and SCX cars, and most Carrera cars are the least expensive to buy new. Some of the less popular cars like Fly Vipers (or Vipers of any brand for that matter), Fly Starter Series cars, and most brands of F1 cars can be purchased at reduced prices. I don't care much for the Carrera cars, they seem to require too much modification to make them perform well. I'd like to use cars that would be a good durable foundation to start on, that work well out of the box, but can be refined and improved. Cars that have performance parts readily available. I have had good results with Fly cars. Slot.It parts are readily available for Fly cars, and work in most cases without major modifications. I have some Fly Starter Series cars I am working on now. I picked up the Fly Porsche Starter cars for $17 new on Ebay.
I'm planning to have another open track day soon. We can see what types of cars people already have, and try out some different cars to see what looks good. I'll try to have a few different types of cars available to test. I'm looking forward to getting something going for the eastside.
-------------------Bill