Actually compared to the same meat quantity of phoenix worms or silk worms, Dubia's aren't that expensive.
A heck of a lot more than crickets, though. That's true.
Mostly because there's less supply of them. Most pet stores don't sell them,
folks who do a lot of Dubia's tend to end up making thier own colonies, and there's
just less breeders around who can do big orders. Plus, if you're feeding big ones they
take several months of care to reach that size.
On the other hand, once you start feeding the bigger ones, the amount you'll be going
through is much less. Rico (about 9 inches long) easily goes through about 40 little dubia's
per day (~20 per meal). Mellow though (14 inches), who is getting medium+ sizes, only eats about 10 of
those per day (about 4-5 per meal and then she's full).