OP, the routes you mention are all from Europe to NA. Are you also asking about ex-North America? As pointed out above, it is generally cheaper to originate in Europe.

When the YYZ-AMS route started I got it for about $1400 CDN each way (P). I’ve done several other routes in the last couple of years (including this year) with each half being <2K when two travel together. Someone on FT indicated that they believed AC was matching a companion fare offered by the competition. Years ago I recall getting LHR during the summer for $800 each way (on a return tx).

The exception, for me, has been LHR. Since last summer I have been unable to get anything reasonable, even booking months in advance. I was watching this route for late fall 2019. It had been about $3200 for the outbound (on a return fare). It dropped to $2800. After the recent “fall sale” the outbound went up to about $5600, the return portion was similarly priced. The load didn’t seem to have changed. Being flexible with dates made no difference. Upgrades are also much harder to come by than in the past for this route.

Another data point — yesterday I saw a return fare Toronto to Narita in J for apx $2400 via Helsinki (Fin Air). Stopover in Helsinki possible.