Prices highly depend on complexity of each task. For example, adding a simple clothes like t-shirt to a base with simple toggle would cost 20$, but if avatar has other clothes you need it to work with (for example a bodysuite under t shirt, and backpack), rigging for each combination would add to price, and it is unique for each case and each prop. Make sure you decide witch combinations you want to work together, to save on commission price.