Perhaps the 30s set could be the subset instead of the rough drawing cards or something like that.
Wouldn't that increase the price of the set dramatically? In effect, it would be two 30 card sets - 60 original paintings - put together.
$250 - $300 per set might be suitable for dealers, but it is definitely out of my price range.
Why not do reasonably affordable 9 card mini sets for the 30s, 40s, etc., along with a checklist puzzle for each set?