If you weigh the mostly full can and subtract the weight of the empty can you can ballpark how much the bedliner added to the guitar.
I don't think that would be very accurate, as I did a bit of practice on a test piece prior to actually painting the guitar. If you do your prep work right and you don't waste as much by testing, I'm sure you could achieve a finish like this for about $10 (1 can or bed liner).