Question is..... if this is for flatbed printing, why worry about it. Sure, you want a good product, but if they don't wanna use a good substrate, why should you knock yourself out to make a piece of sh!t beautiful ?? It's all relative.
I just made arrangements with a guy this afternoon to letter his truck next week. We had a cancellation and I have an open window of a few hours net thursday. He sent me files for what's going on the truck and asked for the price to do it. I specifically said, how much to make the graphics and put them on and I said, in our shop. He wrote back that everything looks good and sent me his credit card information for the deposit. Before I processed anything, I called him to verbally confirm everything. Then he says, now you're picking it up or doing it here ?? Nope. That'll cost ya extra. That wasn't figured in for lettering it. Then I mentioned.... as the quote says, the truck must be washed before bringing it in. He said, it's clean. I said, we only give it an alcohol bath. That... does not remove dirt and certain other contaminants. If you want us to wash it, that's also an extra cost. People don't listen or should I say don't read very well or they just opt to tell ya they didn't understand after the fact.
Why quote a cheap material then spend money and time making something nice for someone who is a cheap d!ckwad ??