I was going to have a contest to see if people could guess how much a ebay auction posted would end up going for would posting a topic of this sort be against the rules as advertising for said auctions or no?

I'd say it's okay as long as it's not your auction.

...or does that make you not want to play this game anymore? ;)

how would one know its not my auction though?

Link to auctions that say only ship to the US.

Ta-da, problem solved.

k contest posted.