Since adopting a more "paleo" type of diet (real food, plenty of meat and eggs, fewer carbs, very little grain), I've found three machines particularly useful: my freezer, my crockpot, and my microwave.
I bought a five cubic-foot freezer at Sears for around $130. It's a half-size top-loader. This enabled my wife and me to purchase half of a grass-fed cow for just over five dollars per pound. I've also purchased bacon, fruit, and other meats on sale, then frozen them. The cost savings for food far surpasses the cost of the freezer and the electricity to run it.
We bought a crockpot at Sears for about twenty bucks. I was unsure whether I'd really use it much, but I use it often and love it. Here is a photograph of ($2 per pound) chicken breasts cooked in the pot with a jar of salsa, then shredded:
Last night we oven-baked a sliced onion with olive oil and salt, which went great with the chicken. Tonight we'll probably eat it with guacamole and sour cream.
I've also used the crockpot to cook several pounds of bacon pieces, beans (not very "paleo" but at least very well soaked), whole chickens, and soup. The removable ceramic bowl is very easy to clean, and I love the fact that I can just plop the food in and leave it for hours at a time.
The third machine is more widely used by Americans: the microwave. I use it often to cook eggs (as I've mentioned. A single egg in a ceramic bowl cooks to perfection in about 45 seconds. More often I make "egg bowls." Typically I microwave a couple of frozen one-inch cubes of vegetable puree (usually cauliflower with spinach or broccoli) for a minute by themselves. Then I add precooked sausage (or bacon or whatever) and two eggs, then microwave at short intervals (30 seconds to a minute), stirring in between, until it's done. Add cheese if you want. Not only do I love the results, but the egg bowls are extremely easy to make and clean up. Here are a couple of pictures:
To me, freezing good food, then cooking food in modern appliances, represents the perfect marriage of wisdom from the ancient past with modern technological sophistication.
(See Ari Armstrong's blog.)