How much does it cost to lose weight?

As 2007 gives way to 2008, many people are going to resolve to finally lose weight, and, tired of unsuccessful diets, many of them will sign up for one of the popular dieting plans out there. But diets are expensive. Want to know just how expensive? The Consumerist recently looked into this -- here's what the popular diets cost per month on average:

• Atkins Diet: $402
  
• Diet To Go (1600 Calories): $524
• Diet To Go (1200 Calories): $468
• Dr Siegal Cookie Diet: $224
  
• Dr Sears Zone Diet : $371
  
• Jenny Craig: $551
  
• MediFast: $275
  
• NutriSystem: $294
  
• Ornish Diet: $299
  
• Slim Fast: $310
  
• South Beach Diet: $314
  
• Sonoma Diet: $274
  
• Weight Watchers: $387

Wow -- that's a lot of moola, and some of them don't even include the cost of food. What do you think -- is it worth it? Or are we being ripped off by the diet industry?