There were no dots and I had full regen. It was about 0C and the car had been driven in that temperature for about an hour. Even if it was cool, which it wasn’t, it doesn’t stay cold forever once plugged in. This issue happens to me in the summer too. When charging first starts, like today, the kw rate leaps up, then shortly thereafter drops to a number much lower than the maximum of that price tier. So today I spent 87 minutes at 25 cents per to get less than half a charge. 223 kms to be exact. That is insanely more than gasoline and it happens to me all the time. It’s not the exception. It’s the rule. In any season. Those 223 kms are really 120-150 kms or so because of winter range loss. For $21! Supercharging isn’t cheaper than gas for me.
It sounds like you are using supercharging as your daily charging...which you aren't supposed to.
Anytime you are supercharging in excess of 50% SOC, it will be greatly reduced. There's plenty of curve examples on this site that show how supercharging is very effective from 0% up to about 50%, and then once you hit 70% or so it's pretty slow.
Ambient temps of 0C also reduce the rate (due to your car and simply due to the rest of the equipment). It takes 1-3 hours of driving to get the battery warm enough for full supercharging rates, well in excess of what's required for no regen dots (think about how much more power supercharging is than regen).
Also, it's partly Canada's law that is a problem since they are the ones that enforce that kind of pricing. Most places Tesla charges by the kWh used. So complain to your local lawmaker to get that changed, nothing Tesla can't help you there.
If you want to actually test this properly, get down to around 40km or less range left on the car on a warm day (10C+) and see what the rate is. If you are still less than 100kW then either go into the service center or call Tesla about that station.