Those are clients you probably don't want to work with anyway. The best clients are usually the ones that have a problem and need you to solve it for them, it's then up to you to use your expertise to deliver that solution. You are the professional and similar to lawyer or doctor it behooves you to do what's in the best interest of client when it comes to your technology choices. Plus if they know the technology they want to use (and often how much it should cost) there's an entire race to the bottom market that addresses this--freelance/gig boards.