About $150 every two weeks . I have a family of four..DH and two daughters age 7 and 8. DH and I eat low carb, the two girls eat lower carb. This also includes household items such as laundry detergent, soaps, cleaners, personal hygiene items (it's amazing how much shampoo two girls can go through!), etc..so it's not all food.
To try and cut costs, I always shop the sales and base my menus on what's on sale when I do my shopping. For instance, this week I can get pork steak/roast and ground chuck for 99 cents a pound and a 10 pound bag of chicken leg quarters for $2.50.
I will also shop more than one store if the prices are good enough to warrant a second trip. For instance, I can get butter for $1.29 a pound at Aldis and cheese is usually much less expensive there as well, so I'll make an extra trip to get some things from there instead of paying $3.50 a pound at the other stores.
Overall, I think it's been a trade off as far as my grocery bill goes; it's not really that much higher. Yes, I buy more meats and cheeses, but I'm also buying less junk food and highly processed/convenience foods.