I find stuffed peppers are cheap, filling and everyone in the family likes them.
Use 4 green bell peppers, cut in half long way and take out the seeds. Mix 1 pound of ground beef with 2/3 cup crushed pork rinds (measure after crushing), 2 large eggs and black pepper. Mix really well and divide among the pepper halves. Place them meat side down in a large deep skillet and brown really well, then flip over. Pour an 8oz can of tomato sauce over the top, cover, reduce heat and simmer for 30 minutes until the meat is cooked through.
You can sprinkle a little cheese on top right before serving if you like.
For 6 servings this is approx 5 carbs per serving.

Cost breakdown will vary depending on where you are.
Bell peppers $1. for 4
1lb ground beef $1.75
Bag store brand pork rinds $1.
2 eggs $.25
8oz can tomato sauce $.25
Total cost for main dish feeding 4-6 $4.25