Its been a looong time ago, but I had a Glock frame duracoated for about $150 or so. It seemed to hold up well for me. With all of the different options out there now, duracoat should be relatively inexpensive I would think.
Brownell's had duracoat kits for about 30 bucks last time I looked. I've heard it's not too hard for a DIY, but you have to make sure the frame is clean and free of oils to get a lasting finish.