i would get another but gas would cost more to go to the other side of town then to get my 3 dollars back....
Good lord... How large is your town? Even if your car only got 10MPG, and the store was less than 15 miles from your house, it would still be worth it. Honestly, if you don't start with a working unit, then you won't get very far.
Do your math again. Using your numbers, he would use 2-3 gallons and at around $2 per gallon, that's 4-6 dollars compared to 3 dollars.
skylarkoz- Try pumping it really fast. When I first got mine I was majorly bummed cause it wouldn't work. It took me about an hour of searching to find that I just needed to pump faster.