That would put it at maybe twice as expensive (or even slightly more) as a non-restricted diet. Is that a fair assessment?
A lot of the popular Asian hotspots have gotten clever over the years, and are no longer afraid to charge foreigners an enormous premium. In the last year alone, I have had to walk away from numerous local sellers because they've gotten extremely greedy and won't accept any bargaining. If you know the local language, it helps a little.
I think if you're serious about making the switch, you first have to look at what you're eating right now. Is it healthy? Is it environmentally friendly? Does it make you feel good? What will you eat instead of meat? Do you even need dairy in your life or are you consuming it out of habit?
When I first started out I had no idea what I was doing, and I sort of winged it. But, gradually, I have learned to appreciate the many different varieties to food that I would have otherwise replaced with a slab of steak or a chicken breast.
One of the ways I solved this is by being comfortable to have meals that consist of nothing but raw food. So, raw nuts, raw vegetables and fruit, and legumes whenever I desire. But I also try to look at it realistically. For example, a tub of Kale Powder (120g) will set me back around 20USD. But, how likely am I to consume that tub in one day? In fact, it will last me for up to 4 weeks. The same goes for 350 grams of Hemp Protein. It's 20USD but I'm going to be having that over a period of at least 2 weeks.
One difference between Asia and Europe is that in Asia I can get a much bigger variety of fruit, which is generally my go-to food besides everything else. But even then, I never leave the supermarket having spent more than 30USD for 4-5 days worth of food.
If I had to be specific, for the entirety of a whole month I'll be spending about 250-300USD on food. I'm honestly not familiar with other diets and not sure how much they can run up over a month. What I do know is that I never have any leftovers. Everything gets consumed one way or another.