While you do get what you pay for, I have used a primer (Transtar 2K) that was 1/2 the $ of PPG and netted very good results. What you look for in primers is film-build, solvent resistance (how "absorbant" the finished product is...less is better), and viscosity. Less viscosity with good film build makes it easier to surface out. The Transtar stuff did not require a sealer before topcoat. More $ saved. I did find out it didn't like reduction...made it "gummy" for dry sanding.