So you're going to be out $100 either way to get the frame blasted. If he's only going to charge you another $100 to powdercoat it, that would be the way go to. If you factor in what it's going to cost you to buy primer, paint, masking tape, your time, etc., that $100 for the powdercoating is going to be a bargain. And powdercoating will outlast paint for sure. You can easily save $100 somewhere else on your build.
In the end, you have to ask yourself, "do you want it done right, or right away?" Powdercoating is getting it done right...