I like the simplicity. Obviously your site can only get better. One thing that would interest me in upgrading to a paid account is the opportunity to select how much I'd would like to spend on the food itself, is there any way to take in to account local food prices? Keep it up!
If there is no automated price scrapping based on the local stores in your area, I think an averaged out "Walmart Price", or "Kmart price" would do just fine. I'm not too sure what the price difference is in Walmart stores across the US, but i'd guess it's not that bad.
I guess that if you notice that price databases to be lacking, you could get users to crowdsource it. Even if only serious power users would fill the numbers at first to make them more exact, it should get the ball rolling.
