The Myoplex bars are meal replacements, with the proper balance of protein and carbs, along with a wide variety of vitamins. Kashi bars have 100 more calories and twice the sugar, but less vitamins. Luna bars might be a closer match.
I used to do BFL and the best price I found for Myoplex Lite products was at www.vitaglo.com
though it's been several years since I've ordered from them. If you have a GNC Gold Card, you can get Myoplex Lite products cheaper at Drugstore.com. I'm not sure if their prices are the same as if you bought them at a GNC store.
My son is getting ready to do BFL. He's very thin, but wants to get in shape. I agree, the plan is very appealing because of the large following of "real" people and they seem so successful!