Wondering this as well.

I would say the first 3 chalk it up to not-so up-to-date currency conversion/rounding?

That expedia.com one I can't explain. I've encountered this kinda stuff too, which is why it's always worth looking. The biggest benefit to using the AC site itself is it makes changes including simple things like seating easier, interacts better with the app, plus you can use codes for discount/travel options.

But when using the OTAs you can also get routings AC won't necessarily offer. Yours in this case is easy, but I was going YYC-DFW-YYC and got offered a better and cheaper itinerary on expedia than on AC. AC seemed to insist I go YYC-YYZ-DFW rtn, but a flight that worked much better for me YYC-YYZ-DFW-IAH-YYC was on offer at expedia, so I went with it. I lose that extra bit of bonus points from the CC, but oh well.

You cannot use logic here. Its simply not fair!!

AC is best in your mind, because you don't use a value proposition.
Also AA/Delta/UA/Jetblue all have premium J class and all of them beat AC, so perhaps you might want to review who has the best J class?

Except it's false logic.

Can't fully the explain the Expedia thing but the difference in price between the the Canadian and US Editions of AC website, even after factoring in exchange rates are due to tax differences between Canadian and US point of sale. Canadian edition will have US international transportation tax whereas US edition will have US domestic 7.5% transportation tax and ZP flight segment tax.

I have not flown Delta in forever and JetBlue never, but UA and AA's J class on short haul flights definitely do not beat AC (at least not in terms of comfort and IFE - price, now that is a different story entirely)

Sometimes you can pay UA pricing and fly AC.

UA had some awesome biz class fares from YYZ-IAH-CUN this winter and you could fly the YYZ-IAH segment on AC metal.

I love those CRA-705 flights done those twice in the past month, IAH-YYC and IAH-YYZ, seat 12A and I'm home!