Hello Karl & welcome to the forum, several years back, one of the pet industry magazines tried to get some numbers on the then market for SS cages, but the then big two manufacturers were tight lipped in the numbers dept., then the availability of SS cages from China has made them available to more owners than before. Where there might be a market is in specialized settings, like small zoos that are not in a position to create large aviaries...and...there just happens to be a member here who used to be with a major NYC zoo, who might be able to point you in the right direction to become acquainted with that industry.....
I have a friend in the laser cutting industry & we talked about that niche market, but gave up on the idea, because unless you can offer a client a model to see & feel, they are often lost on conceptual ideas.....we were even working with materials for a project where the client had gone belly up, with 80% of the project paid for, so we had a lot of wiggle room to work with, but still couldn't justify more than two builds.....
The numbers are 5 years old, but I think I've still got them somewhere, PM me if you've got any other questions.....