Add that almost all the same artists are on all the sketch card sets.The uniqueness is gone then. So all that is left for now is characters and quality of the cards. I never wanted my cards to ever be collectors items. Maintaining a certain quality over several sets is very difficult and I would rather have some wiggle room in my quality than be hampered by expectations. Plus when I do go slightly hog wild the end buyer appreciates it more. This also helps retain my AP value as i don't do many and the ones i do are far superior to almost any inserted cards. There are some really nice paintings I did that I'm sure could top or equal some of my AP's.
Value is based on scarcity. Even if a top name does few cards for a set, but does a lot of sets the scarcity is still gone. I was asked by RA to be an incentive artist but declined for the reasons stated above in my posts.