Thanks for the quick response - really interesting and will see where this goes. Always a lot of nuance in these matters, but as you note this seems to be more than the standard garden-variety DCC issue.

This actually seems to be a manifestation of a more common issue that I've always wondered about - when a property won't quote in local currency. Searching this property, you can see the results in USD, and you can change the display currency to BYN. But even when showing BYN as the currency of choice, if you click the details, the full rate (with taxes) is shown as denominated in USD. I've also seen this even within markets - I'm thinking of some other Eastern European countries I've been to where even for a given city, some rates will display as local currency and others dollar-denominated. In the latter case, because they're quoting in USD, it's basically giving them carte blanche to pick their exchange rate as happened to the OP. What drives this on a city / country / property level, I'd be curious to know.