Originally Posted by NHFL9
This is correct. 5,000 SkyMiles each way for full-fare, 10,000 SkyMiles each way for a B or M class ticket. Other than that if seats are open day of departure after all upgrades have been processed, they will sell upgrades at the gate for approximately $100.
But note that you can only buy a UG at the gate if you are not on a L, U, or T fare.