The cost of replacement feet varies greatly, and some units require extensive disassembly to replace the foot. Many units, especially smaller ones, will be less. Winders attach to the bottom of 35mm SLR's. They generally have limited features and do not have a release button as part of the winder. Motor drives are similar to winders, but usually have a release button as part of the motor drive which can be used to operate the camera.
Some professional models are higher.