It is true that the only producer of Medifast products is... Medifast. Consequently your choice of what you buy is a little limited. But the choice of how and where you buy your food is not.
Deli meat can be used to make great lean and green salads but it can also be expensive. You can prepare your own deli meat for a fraction of the cost. Buy a whole chicken, turkey or cut of beef and roast it, slice it and freeze it yourself. Make sure you drain the fat away during the cooking process. A good way to do this is to cook it in a pan with a slightly raised rack so that the fat can drain to the bottom. This way the fat can drip thought the rack into the base of the pan leaving you with lean meat. Cover the top of the meat with foil to avoid it drying out.
Store the meat in Tupperware or a freezer bag. You will need to separate the slices with plastic to stop them sticking. Alternatively you can move the slices around after they have been in the freezer for about two hours, by which time most of the moisture that causes them to stick has frozen. However it is easy to forget to do this so layers of freezer bag plastic may suit you better. Simply cut a freezer bag into meat size pieces with scissors (use ZipLoc bags or cheap alternatives) and layer between each slice.
As well as being cheaper, home sliced meat is healthy too as most deli meats contain the cancer-causing chemical sodium nitrate.
Vegetables that are in season are generally the cheapest and savings can be made by buying in bulk. Specialist fruit and vegetable sellers or markets will often, but not always, be cheaper than supermarkets so it may be worth investigating if you have such options available in your area.
Many vegetables freeze well; in particular peas, spinach, broccoli, cauliflower and most varieties of beans. They will thaw at room temperature in 30-40 minutes; but can be used straight from the freezer if you are cooking them. The vegetables may become a little softer after freezing; this is because the water in their cells expands slightly causing many of the fiber walls to burst.
There is evidence to show the buying frozen fruits and vegetables is better for you health as well as your wallet. Frozen foods do not have the same time to decay as fresh foods and so the nutrients are trapped in at an earlier stage by the freezing process.
This is also why you shouldn't buy vegetables that are wilted or old – they will have lost a lot of their vitamins.