Originally Posted by FrozenK

On a mountain bike you wouldn't need a new wheel. Just a shifter and derailleur. It will still cost you more than $82, though. Probably close to $200.

On a road bike you may be able to get away with not buying a new wheel. You'd have to use a mountain bike cassette, though. But I think SRAM 11spd road is compatible their mountain bike cassettes.