I'm quite happy to pay £4.50 for my sanity and therapy LOL. It's a lot cheaper than going to see a psych. TBH, going to class each week keeps me on track. I need that day of reckoning each week. I need to be answserable to someone other than myself. We have a good laugh at our class on a Tuesday morning.. it's somewhere I can socialise without worrying what other people are thinking about me and my size.
Some people can stick to the plan without class, and I envy them, but if you're getting dispondent, maybe a few sessions in class would give you some encouragement.