Good idea. I find the picture confusing though. I think it would be better with simpler lines. Perhaps if the car were clean. (This is not meant as a joke or an insult, just a comment. The streaks on the car make this image more confusing than it would be with clean lines.)
the black and white make it difficult to distinguish the gas bowser from the card (perhaps could use a wash!). I also would look for prices in the image (with your title).
Nice image, but not really evocative of the prices. I'm in the middle on this one, it doesn't seem like it would make it past an editor, but it's a nice shot.