I've never understood buying something and then keeping it in the original package, because I never consider resale value. If I buy something, I want to play with it.
I buy 2 and keep one in the box.
Usually though its to keep one set intact while my boy loses the pieces to the other while playing with it.
Are there really any Star Trek figures that have gone up tremendously in value over the years?
The only figures I am aware of with any real value are the 6 Mego 3.75 inch aliens, of which I have 5. They quickly rose in value and have held that value over time. Loose they go for about $75, MiP $150. Due to rarity I have seen people try to get more than $1,000 on Ebay. Back in '91 I had a dealer at a con try to sell me the set of 6 for $300 each. That might have been ok for MoMC figures then, but his cards were not mint and I told him so. He would not budge on the price and ended up taking them back home with him.
Another reason why I prefer loose figures.