OK, why on earth does a 35" tire that fits a 20" rim cost 374.00 when the same diameter tire with a 15" rim is around 150.00

Your paying more for less tire. I would love to get a set of 20's but this might be the stop sign.

 

there is a lot more technology that goes into the bigger rim width tires... or some crap like that.

 

Also, I am sure they will sell a lot more 15" than 20" which are relatively new. Higher volume, less cost.

 

Large wheels are very popular. Therefore, people are willing to pay a preminum price for them, as well as the tires. As competition increases, price will go down. A few years ago you could not buy a 20 inch tire for less than $200.00. The same is true now with off road tires for 18 to 22 inch wheels. As more and more people start making large off road tires for large wheels, the prices will slowly go down.

 

+1 Especially since the 35x15 has a lot more rubber!