Wow, that's really expensive for use of the existing plaster surface. You are quite right that a roughened surface works better as it allows the epoxy coat layer to adhere well. Then all they need to do is apply the AB thermopolymer and make it smooth and seamless....that's the hard part, making it look good since dimples and bumps in the surface will be accentuated.
Still, $16k for AquaBright on old plaster seems a little unreasonable to me....
I agree completely. If the stuff is truly that expensive, it's going to be difficult for it to catch on. I think it needs to be competitively priced with high-end plaster. At least in my area with this particular installer, it's not.