No doubt the cover is back dated. That is quite common for those philatelic cancels, I saw it first hand at the Vancouver 2010 Olympics.
The turn around for buying Picture Postage stamps is less than two weeks or even 10 days from personal experience.
That leaves plenty of time to get the finished product on
ebay by January 20, the date it was listed.
The value is whatever a hockey thematic collector is wiling to pay - it is no different than any official first day cover, they are never really cancelled on the day of issue or even in the "location" city.