you spend on all the usual groceries, take out food and restaurant meals you pay for over the same period of time.
this all figures out to a diet plan that is cheap, works and as long as you stick to it and do not cheat, will help you lose weight at your own pace. that will be the pace that is right for you, and maybe not the same as someone else you know. but it will mean you lose weight as easily as is possible and that's what makes it so popular. 