I do Jenny Craig, which is much more expensive because you have to buy their food (fortunately, it's really good). We have to supplement the food with vegies, fruit, and dairy. I guess for just me, it comes to about $180/week. but in NYC that's still cheaper than dining out as often as I did, and comparable to grocery shopping. But yeah, WW, which I've done in the past, isn't very expensive because you still buy real food at the grocery, can use coupons, etc., and you do eat less. At JC, they talk about "volumizing" your meals - which means that you add volume with vegetables, salad, etc., so that you feel satisfied but with healthy stuff.
It helps to sit down with a budget sometimes when you're trying to lose weight and look at all the $$ we spend on crap that has no nutrition. I know I have personally wasted tons of cash on food that was unhealthy and fattening.