I have to agree with your friend, it is more expensive... At first. Getting ready with all your flours and substitutions (if she no longer has them) is pricey! Buying meat and fresh veggies is much more expensive than government subsidized grain and boxed/shelf food. When I started saving money is when fat adaptation kicked in. I am one hell of a cheap trip to the market now. Half my week is spent fasting! Either way, I'd rather spend money the first couple months on keto than down the line on co-pays and prescriptions.

This came up in a couple discussions for me recently. I have been lower carb for a few years and keto since August 2016. I find it APPEARS to be more expensive because individual food items cost more. However, in reality, my food bill is down at least 1/3. Here's why:

When you eat the cheap carbs (i.e. bag of chips), you are hungry an hour later, so you have a second bag, and third, and so on. When I eat a handful of macadamia nuts (far more expensive), I am good for several hours because the very high fat content is satiating.

I also eat clean, not just keto. This means even when I do eat carbs, they are things like fresh spinach, celery, fresh steamed broccoli, etc. which don't have the added sugars and are higher fiber which also satiates.

Because I eat clean, I eat at restaurants far less. Clearly eating what I cook is much cheaper than restaurant food (and it tastes better). To be clear, the reduced food bill mentioned initially is only groceries. If I included this savings, I would have to say I am saving closer to half.

Once fat adapted, I found myself naturally doing intermittent fasts (skipping breakfast) just because I wasn't hungry. Later, I incorporated longer fasts of 1-2 days without hunger. It is hard to say eating zero costs more than eating crappy carbage.

Getting rid of all caloric drinks and sticking to water, tea and coffee makes all meals cheaper. It is ridiculous how expensive Coke can be - especially in a restaurant.

Not cutting the carbs also has that nasty cost down the road of increased medical bills that really should be factored in as well.

Personally, by eating this way, I have gone from steak being a rarity in my house to something that is eaten at least once a week and I still spend less on food.

Those who spend more on this WOE typically do so because they are eating the LC junk food (i.e. Atkins bars). If eating correctly, within a couple months, I think you will find you have no need for snacks 95% of the time. The key is learning to recognize the difference between true hunger and the habit of eating at "snack times" or out of boredom.