So is this not a thing? I'm Canadian and during these past few sales I bought a few things but when I looked at my bill it was not the same price, it was nearly double! The only answer is that the games prices were in American, but I thought GOG went the way of Steam and got regional prices for their games, including Canadian... is that not a thing?

Only Witcher 3 is cheaper in Canada, as far as I know.

Nope, not as yet. The only foreign currencies they support so far are the U.S. dollar, the Euro, the British pound, the Russian ruble, and (IIRC) the Australian dollar. So, yeah, all prices for Canadian customers are displayed in U.S. dollars.

And Grilledfish is right, so far the four The Witcher 3-related items are the only ones in the store to be regionally priced in Canada.

I don't think you can pay in Australian dollars.

Interesting, I didn't know that. Was the option introduced with the other local currencies or was it added later on?

It was here since the introduction of different currencies. No other currency has been added since then though.