Cheap, high in protein, tasty, and fast-cooking, lentils are one of the heavy-lifting heroes of the green pantry. (Anyone remember The Young Ones on MTV? My first exposure to lentils was watching Neil, one of the characters on that show, reviled for his love of lentils.)
Organic lentils are about $1.50 per pound, give or take. Conventional lentils are easier to find at the local market and are even cheaper than that.
26% of the calories in a lentil are from protein. So for 100g of lentils, there are 101 calories, and 26g protein. 100g of lentils is about a half-cup, cooked.
There are 453 grams in a pound, so at $1.50 per pound, lentils cost about 1/3 of one cent per gram. So for 100 grams, you will pay about $0.33.
For 100g of 85% lean ground beef, there are 256 calories, and 26g of protein. For beef, 100g is a little less than a quarter pound. So if you started off with a 1/4 lb burger patty, 100g is probably what would be left when it was cooked and the fat drained off (maybe a little less).
Beef prices vary a great deal, depending on the quality of the meat, the amount of fat in the meat, etc. But in order for your meat to be comparable in protein content and cost to lentils, you'd need to get your meat for $1.50 per pound.
Now, I don't know of anywhere in Alamance County that you can get decent quality meat for $1.50 per pound. Yuck. If you're looking at organic or locally grass-pastured beef, you're not even going to be able to drive into the parking lot for $1.50. Forget it. And that's the way it should be. Cheap meat is not worth the other costs.
Here is a page that discusses the various environmental claims about how much it costs environmentally to produce beef. Here is a page that disputes some of the numbers. Regardless of how many gallons of water or pounds of CO2 are being debated, it is very clear that lentils beat beef on price, protein, and environmental cost.
My recommendation is to eat lentils or other low-cost plant-based protein on a daily basis, save up for really good meat, and eat that on a special occasion when you can really enjoy it and feel good about your choice.
Pocket: 5, Planet: 6, Win-Win: 21