Currently all product prices in In-Commerce are stored in primary currency.
For example 100 in database means:
- 100$ when USD is primary currency
- 100 ?. when RUB is primary currency
Also In-Commerce does automatic currency conversion (before it is displayed to user) based on same rule: from PRIMARY to user-selected.
I'm proposing to allow PRIMARY currency be specified in each product separately (if there is a need). This of course would only affect currency display on product detail page, but won't affect subtotal amount calculation and such code.
These other things can be done as an improved that idea version.