No, it's totally legal. Cheeky..! but legal. It's his picture, he can do as he pleases with it (legally). Would be different if the photo was offensive, or if he was trespassing whilst taking it, or if (in some cases) it constituted a significant invasion of privacy, but just a car at a show, even with the plates in the picture - nothing you can do except moan at him.
You can take your own photo though and save yourself £1.99
Can't think who buys this crap, but looking at his previous sales, he actually gets sales of photos of random stuff.... odd.