I built a drum roaster several years ago, I called it the redneck roaster, I used a foreman style grill and a paint can (new can no paint ever in it) and stainless steel screen, it easily did a pound and cost me about 125 tops to build.
on your question though, how big do you honestly think the market is ? If you are roasting more than a pound at a time, are you really 'hobbyist' then? why not do several batches of 12 oz, if you are doing 15 batches a week, again, you are not a hobbyist, you are more a commercial roaster, and the behmore or any other 'hobby' roaster won't hold up long at that kind of use... you complain and warranty issues arise. Which is why they make 1500 dollar roasters that CAN hold up to that amount of work.
Aaron