Scamming inside the confines of certain game activities is the norm. It's not good sportsmanship, so to speak, but people do it and the GP have little control over it. You can search for the Terms of Service for graal - Scamming is dealt with when it's through the official trade feature of the game (which classic server does not have). When you're talking about people who are offering to trade gifts, it becomes a question of if you know them well enough to trust them.
Personally, I never gave a gift in hopes of getting one in return. Not even to my best buddies. It's absolutely against the spirit of the holiday, so you're getting what you deserve. If you have some cash left over at the end of the event, go toss some gifts in the secret santa (by church) and you're guaranteed to get the same in return.