Cavalary: Thank you for all the work. But I'd say no need to rush, since these will probably change quite rapidly for a while... And maybe massively if/when GOG will update the exchange rates from the artificially lower ones that are now.
This was just a bugfix for something which I was actually doing wrong, unrelated to GOG shenanigans; For products where the previous all-time low price in the US ended in the morning of 29th, I treated the initial Romanian/Hungarian/South African price gathered in the afternoon of the 29th (so without a discount) as the all-time low, so any future discount was treated as a much better improvement than it really was.
Of course comparing current prices to fictitious previous prices is a silly thing to do anyway, particularly with that built-in 20% across the board price reduction - but at least it's internally self-consistent, where the bug was a weird one-off.
Cavalary: On another note, found myself thinking of wishlists when I woke up today, and this may tie with pablodusk's earlier idea as well. What about a "I don't know" or "Maybe" wishlist option, which in case of people like him, who want to have an extended wishlist on GameSieve and a limited one on GOG, may benefit from a wishlist import setting that says don't remove games no longer on either wishlist or library but switch priority to I don't know (or Maybe)?
I can very much see the use; a way to identify wishlisted games which you removed, and maybe automate setting priority. I'll need to thoroughly think through the way this'll interact with things, though. E.g. what if you'd painstakingly set priorities for everything, and then turn on this setting? There's a definite risk of data-loss.
...
Yeah, after pondering this for a few minutes, I'm afraid I'm going to make this a long-term thing, as it'll probably need to be a completely separate field from the priorities.