Next time you have currencies in a chapter, please make them an area hotlinked to a picture hosted locally on your site. The picture must be auto-generated from exchange rates fetched from stock markets' APIs for all currencies. Then a picture is generated for every possible currency. When a user is reading the chapter, the correct picture is requested based on a combination of IP geolocation and Accept-Language browser headers, and then the correct amount is displayed for yhis local currency.
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or it could be an OCR plugin living in the user browser and capturing currencies encountered as pictures when the user is on mangadex/chapter urls.