@Ghadage Aniket When using currency field in JSON formatting and concatenating some text to its value, it gets converted to string. I searched and tested, however, no such function was found to convert it back to currency in JSON formatting and append the commas (,).
I also tried using Calculated column like the below, same result returned.
A similar thread for your reference:
https://techcommunity.microsoft.com/t5/sharepoint/currency-field-formatting-with-json/m-p/1514591
So, currently, it seems that no way to change the currency format. For this issue, I suggest you submit a feedback on this portal, it is a place for customers provide feedback about Microsoft products. What's more, if a feedback is high voted there by other customers, it will be promising that Microsoft Product Team will take it into consideration when designing the next version in the future.
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