Price has come down in the past few years on wild bettas. There's more and more breeders who are pumping out babies from some of these wild strains like rabbits. It's not Splendens cheap but alot more afordable than years past, that's for sure. Tank raised wild bettas are also more resilient to disease than their wild caught counterparts so that makes it alot easier to keep these fish now as well.
Sorry for going OT.
Why are they more rewarding?
Check out my 120-P (2nd to last page) in my sig. You'll see the "King of Bettas" there.