I feel for guys who produce fabulous themes that just don't sell.
Maybe sometimes developers need to be more business savvy.

If you look at the time spent producing a theme and add the support time and then work out the hourly rate that your sales bring in... most developers would probably look for other ways to pay the bills.

Most developers must think that their next theme will be the one that breaks through and sells like hot cakes, but over the time that I've been an affiliate for WordPress themes I've only promoted one that sells like crazy... any guesses?