Property:Monetary amount

From semanticweb.org

This is just a Number, but uses the currency service to provide currency conversion links. See MediaWiki:Smw_service currency

It ignores the currency "unit" after the number, but the unit is important for the external currency conversion service.

The alternative is to define a custom Type:Currency amount that uses the special Property:Corresponds to to store currency conversion rates and convert different currencies, just like a Type:Length can convert different length measurements to meters. That approach introduces the ambiguity of when the currency conversion was performed and at what rate.