that's rubbish anon.... A passionate and loyal Port supporter will always want memories of that great day and will be willing to pay for it.
As a Crows support, I'd give you a slab of VB and a lesson in hot-wiring any early model Holden Commodore or Hyundai Excel for the weg.
The thing you'll find with weg and AFL is that they will only appeal to an Australian buyer, thus making it a smaller market. A positive thing about the weg is that it'll appeal to collectors. I work with a bloke that collects wegs, he's now 50 and been collecting them since he was 15.
Value is hard, as I said earlier, a Crows support may pay $5 for it, whilst a Power supporter may drop $50.00 on it, the club may pay $500.00 for it. Who knows???
Insure it for what you'd like to sell it for. A way to increase it's value is to box frame (may sure it's boxed framed and question how they will secure the weg) it and maybe add some pictures from the game (team/game photos) around the outer, but being a poster I wouldn't display it in direct sunlight.
I guess the positives are also it was their first (and fingers crossed only) premership. It also contains the signatures of a Norm Smith Medalist, a Brownlow Medalist, a few All-Australians and from memory it was Hardwicks last game in the AFL.