Today I asked my comics shop owner (Jos) where he got those nice, rare smurfs from. He told me that 'the Netherlands' largest smurf dealer' decided to quit, or at least sell all of his stock, some 15,000 smurfs (= Jos' estimate). He divided it into fifteen sets of 1,000 smurfs and Jos bought one of those sets. So I'm assuming there's more of those smurfs somewhere in this country and/or Belgium, and it might explain why there are so many hard to find smurfs available all of a sudden. There's still a drawer full of smurfs with crutches and in wheelchairs, amongst others at the shop.
Jos, in any case, did not know about the yellow hammer smurf being such a rare variant (*) even though he's something of a collector himself and usually doesn't hesitate when there's a deal in it for him somewhere. Lucky for his customers, I guess!
(*) Fetching $100 on eBay qualifies as a 'rare variant' in my opinion