Why $30 a week?

After Paul and I had been married a few months it became apparent that he had some food issues. He loved everything I made but every night without fail he got sick. His already mediocre energy level dropped, his depression got worse, and every night he lay on our couch in pain. I didn't know what to do for him and I couldn't figure out which foods to avoid so we went drastic.
We started the You Are What You Eat diet from Gillian McKeith on BBC and BBCA and it was fabulous! Paul felt a lot better for the most part and it was extremely healthy- unfortunately it was also pretty expensive. I'm ashamed to admit that our food budget has been 400+ for almost our entire marriage.
Now that Paul's medical issues have been sorted and he can eat everything again, I need to reign it in a little. I love cooking and that's part of the problem. I LOVE it and I'm good at it and I've become sort of a snob about food quality and that's okay but there's no good reason that we need to be spending so much money for the two of us.
Last week I was reading online and I found a whole bunch of people committed to only spending $30 a week on food. A lot of them are single people, some are couples and the idea got me excited. I love a challenge and now I have motivation and a definitive number to keep myself under. I decided we'd start on October 1st, the first fiscal of our monthly budget and to keep myself in check, I'm using the envelope system (I've resigned my debit card to Paul).
I personally know a lot of people who actually live on less than 120 a month for food and I completely admire them. In time, I may try and lower our budget but we'll see how this month turns out.
I want to eat healthily because it makes such a difference in Paul's health and I ought to get over my sugar addiction (because it totally is one of those!). I don't know that I'll post every day but I'll try.
We have a decent stock of dry goods already in our house but I'll try my best to calculate the price of everything that I use.