How many users of Blitz3d have also purchased other BRL software? A great many, I think. So I don't believe that you are correct when you say "who aren't giving them any profit."
You're contradicting yourself - its only a few minutes since you pointed out, and I quote: There are a LOT of Blitz3d users out there. Not all will switch to Blitzmax.
Given that those people most likely won't take a step back to Blitzplus or even Blitzbasic, and there's a free version of Maplet for Blitz3D users, what other BRL products are the die-hard Blitz3D fan base going to buy?