I actually disagree with this reasoning. Why do you think that because they can't be exported that the demand for them would go down? You would think that the demand for them would increase.
I honestly am not quite sure why dumeril's boas aren't as popular. They are really cool snakes, but they still get some size to them. They're definitely no ball python!
But back to the import issue... look at their cousins, the madagascan ground boas. Very similar species and look almost exactly the same, yet their supply is even less than dumeril's which makes them significantly more rare and expensive. These guys are never seen for less than $1,000 each hatching specimen.
Angolan pythons aren't able to be imported anymore, much of which is likely associated with Angola's constant internal conflict. However, these AMAZING snakes are highly prized and valued. These guys are NEVER found for less than $1,500 a pair-- the cheapest I've ever spotted them. I'm actually hoping to get into these little guys.