Where did you get the $21K figure and what model does this correspond to?
Just talking with a friend associated with LEAF and he said due to the falling value of the EURO versus the dollar, the price of Rotax engines has recently dropped and could continue to drop (depending on the politics).
Kitfox is also a distributor of 912 engines. John McBean has posted prices here for them before maybe he would update us on what he is getting now.
I've also heard rumors of a turbo charged, fuel injected 9XX model coming soon directly from Rotax that would be in the 140-150 hp range.