Just out of curiosity...
doesn't refinishing cost around $150 per wheel? And then it's $200 for powder coated? For $50/wheel, powder coat would almost guarantee a non-flaking repair job.
Btw, I usually fix my own curb rash damage and I haven't had flaking yet? See if the guys who are respraying your wheels are using any type of etching primer or adhesion promoter before they spray the paint down. If you spray a thick layer of paint over smooth clear coat, it'll flake no matter what. And are they just spraying that small area or a larger area? I tend to end up misting the entire spoke up to the center cap where I can hide the respray line.
Damn...maybe I should start my own curb rash repair business.