Outer Limits 4x4 Board

This is probably going to be a fairly hard question to answer but what size wheel can you go to before the price for 4x4 tyres starts to grow very quickly?

eg I presume 4x4 tyres for a 21" wheel would be astronomical compared to the same 4x4 tyres for a 15" wheel.

Thanks

Cory

I don't think its price so much as the variety you have to choose from would drop as you go from 16-17