Yeah, Buce likely grows faster emersed, but it is still categorized as a slow grower compared to most plants.
Not sure what plants are most profitable, but pretty much most plants would grow much faster than Buce, and so, you would have more to sell, even if each individual plant/cutting is worth less. For example, even most of the basic cheap plants (common Rotala, Ludwigia, Bacopa, etc) that are worth only 50 cents a stem, or $3 a bunch (5+ stems), those that grow much faster than Buce, would mean more amount to sell and more often, which would bring in more profit compared to the selling slow growers like Buce. Maybe back in the day when Buce was new to the hobby and super expensive, then it might have been worthwhile to grow it for selling. Right now, Buce prices are similar to Anubias and Java Fern.
In my experience, Cryptocoryne, Java Fern, and even Anubias (slightly) grow faster than Buce.
Emersed grown Buce is often sold cheaper than submersed grown. The transition from emersed leaves to submersed leaves isn't as pretty and quick as you may think.