Definitely. Just change your license so if businesses with incomes over $100k a year want to use it, they have to buy the Professional license that costs some appropriate amount (I'm thinking $2000 for a site license or $100 per install, something like that).

As a game developer I've seen a lot of small tools start doing this. Don't try and stop people pirating since you can't, but this way at least people who work at a business who aren't personally signing the checks don't really care if they have to pay a few hundred dollars to use their favorite & best tool.