This is not even remotely close to being true. If recycling wheels, mounting your own foam tires can get the cost down to about $3 per pair if you buy donuts from Japan. With new wheels, the price goes up to about $5-6. Ulti donuts sell for $15.00 for 3 pairs stateside, so even then, the savings are substantial. This is at retail pricing too.

People don't mount their own donuts because somewhere along the lines we got pre mounted tires which had better glue jobs than what most could do as they would learn the process. Over the years we got conditioned to buy premounts and the art of mounting tires was lost in most of the Western RC World.