Update.
I just received a bill today for an additional $57.30 in Brokerage charges for that same motor that UPS previously said would cost me $98.00 in brokerage fees before they could deliver it to me.
This notice warned me that this new payment was now due, and if they failed to receive that payment by mail by Dec 13/22, a 5% late payment penalty would be added to it.
Before complying, I called them up to see if this was a legitimate bill from them, and they confirmed that it was their address. When I asked them to check that amount through my tracking number, they found that it said that all fees on this delivery had already been paid before it was delivered.
They then said to just ignore this latest bill.
It made me wonder how often they ever returned brokerage overpayments.