It’s not an error. Amazon increased by the same amount, at least in Canada.
It might not be because of the tariffs though, it might be because the CAD has dropped quite a bit, probably price adjustments which they do occasionally.
Yes, I believe it is due to the exchange rate. The memory and storage upgrades have increased in price on the Mac mini here in Canada, which reflects the low Canadian dollar. This is also reflected with the M4 MacBook Air. It used to be $250 for the upgrade to 24 GB RAM or 512 GB SSD, but now it's $300. Actually, even when the M4 Mac mini came out, the CA$250 upgrade pricing was cheaper than the US$200 pricing.
2024-10-29: 1 USD = 1.3909 CAD, so 200 USD = 278 CAD
2025-03-05: 1 USD = 1.4381 CAD, so 200 USD = 288 CAD
I was hoping for the memory and storage upgrades to be increased only to 275 CAD, but it makes sense they chose the nice round number of 300 CAD, which provides them a bit of breathing room. On the flip side, they did decrease the base model pricing, so that compensates for that. In fact, for lower to mid-tier models, the M4 MacBook Air is cheaper in Canada than in the US, because of the low Canadian dollar and the lowered base pricing. (I haven't done the calculations for the M4 Mac mini because I already bought back in October.)
Currently, my M4 Mac mini 24/512 GB with 10 GbE costs CA$1404 edu. I pad $1281.50 edu, a difference of $122.50,