RE: CRAWLER KITS-?...
None really, most crawlers are home made.
You can buy chassis kits which comes with a chassis, links, shocks, etc., but youll still have to buy axles, wheels, tires, and electronics seperately.
As for pricing. Axles are about $75 on ebay. Complete set of tires/wheels about $75-100, chassis kit, about $200+++. Or you can build a chassis from scratch for about $30.
Then youll still need an ESC 1-2 servo's, a receiver, and 1-2 motors.
Ive got about $200 into my crawler so far, if you want I can post pics tonight so you can get an idea of how far the money goes.