To add to Jafo's reply, Stardock/WinCustomize has very little if anything to do with how many skins are free and how many are paid skins.
The decision as to whether or not a skin is free is completely decided by the skinner. If he/she is a master.
How true! Stardock may receive a small part of the payment for hosting costs, etc, but the skinners are the ones who decide which skins are free and which are master skins, at which price. At the end of the day however, it's up to the individual as to whether or not they purchase them.
Thing is some Master skinners still release free skins, and there's still quite a few free skins released by non-master skinners, so there is a reasonable balance and plenty to choose from.