What you buy will depend on your carb level, but here's some current prices in my area:

At a regular grocery chain with thousands of weekly price changes, these are some of their loss leaders:

Green cabbage - 17 cents/pound with coupon and $25 order (limit 4 lbs) - or 69 cents/lb without coupon
Point Cut Corned Beef Brisket - $1.67/lb [Flat cut $2.47/lb]
80/20 ground beef value pack (approx 4-6 lb package) $1.77/lb with coupon and $25 order (limit one package) - or $2.99/lb without coupon
Green, Red, Yellow, or Orange bell peppers -$1 each
Chicken legs or thighs (value pack: 4-6 lbs - NOT boneless/skinless) 99 cents/lb

At a cut rate grocery chain:

8 oz basic chunk cheese (cheddars, mozarella, monterey jack, swiss, etc): $1.99
large eggs: $1.35/dozen
Deli sliced cheese (provolone, swiss, mozarella, etc) $1.99/8 oz package
Heavy cream - 1 pint $1.59
Cream cheese - 8 oz 79 cents
seedless european type cucumber - $1.25
broccoli crowns 1 lb - $1.85
Fresh flat leaf spinach 10 oz - $1.19
Zucchini 24 oz package - $1.69
garlic 3 head package - 95 cents
green peppers 3 pack - $2.69
Romaine hearts 3 pack jumbo - $1.99
yellow onions: $1.19/3 lb bag
Tomatoes on the vine 1 lb package - $1.99
Store brand mayo 32 oz - $1.89
Jarred salsa - $1.19
Canned mushrooms 4 oz - 55 cents
canned tomato sauce (no sugar on ingredients list) 4 oz - 25 cents
Pork rinds 3.25 oz - 79 cents
green olives - 99 cents
frozen berries (strawberries, blueberries, raspberries, or mixed berries) 12 oz bag - $1.95

There are some organics available at that store too - prices are a bit higher for those, but still less expensive than at a regular grocery chain.