it's localized for each countries currency but also includes the companies service fees to translate, localize and print the book. the prices will always be cheaper in Yen (or whichever country it came from originally) then in any other currency because they're not paying for it to be translated but also each country has a different process they go through for printing and localizing depending on which company has the license and what resources they need to use. Translated books go through a different set of steps then the originals do.

This is getting an official English release by Kodansha USA btw.
The JP also has 5 volumes ongoing.
https://kodansha.us/series/what-if-i-said-i-love-you/volume-1/