That's a remarkable value on the chassis, including the motors & wheels (and possibly even the screwdriver pictured).
The claw is nice, but requires some heavy mods to get it working properly. No one has reported finding the perfect servo that "bolts right up".
All the parts are imported from China and I think everyone is still making money, even at $15. Elsewhere (on other retail sites) the motors go for $6 a *pair*. The wheels are a couple of bucks. So all things considered, SparkFun may still be making a profit, but it's probably a slender one, in order to sell Arduinos.
Strangely, they show the fully decked-out robot with an $80 13A motor driver shield, when the $25 2A one will do.