And you pay about $100 more for a lower.
But just a reminder: at least for the winter months, you can book berths on the Canadian 1 to 2 months out at roughly half price at
Sleeper Plus class deals. Reservations at those rates are non-refundable, unmodifiable, and not subject to any further discounts.
At this moment, lower berths are available on that page on the full route of every Canadian thru 2/19/23, and upper berths thru 3/1/23. I suspect lower berths may be added for after 2/19 as time progresses.
I don't know how good availability is during the summer months.