Went out with some friends yesterday to TGI Fridays. We split a spinach artichoke dip with veggies instead of chips. It was yummy. It was also two dollars more then the one with the chips. Reason? The veggies have a short shelf life, take more preparation and cost more to buy in the first place.
Same with other low carb options, potatoes last forever, you can buy them in bulk and serve them over a month if you like. Fresh broccoli? Maybe a week. Lower volume, higher price, more waste equals higher menu prices.
Since starting on locarb, my food bills have increased but not incredibly so. However, there are many stages of marking-up in the restaurant business, and costs that register as nominal to the home cook will be exponential to those dining out.