Plenty of things vary by location. Rent and wage have a bigger impact than sales tax on the final price in a supermarket. Yet they are able to coordinate sales prices even when the rent varies a lot, because anyway those are loss leaders and then the rest of items get the proper markup and differentiated prices depending on the location. Just like you have items in the RU with the same promotion prices in countries with 15% VAT and countries with 25% VAT, usually because you want the nice rounding at, say, 399.