Literally the entire development cost. Games don't appear for free. They are developed with the money you pay.
Regional pricing is basically saying that for some reason video games should cost more because you have more money to spend on them.
That's just asinine. Every other industry that tries it gets widely criticized for it. If you want to get more money out of people with more money, give them more stuff. Don't arbitrarily decide something costs more in one country than it doesn't another even though the distribution costs are identical and the development costs are identical between them.