Mike,
I did a search for discount auto paint and it looks like there is no such animal. Some sites call themselves "discount", but the prices are the same as the non-discount sites.
I think automotive paint might be classified as a fair trade item....there ain't no deals. Some paints can't be sold in certain states and Hazmat charges are often tacked on to the shipping so mail order costs aren't the best deal.
The one thing everyone will see as you drive down the road with your truck is the paint job. This is one item you want done perfectly.
Stuart
