Truthfully, I think buying toys in the hopes that the resale value goes up is ridiculous. You'll always end up chasing something, or buying everything, and feeling burned. Big waste of time, IMHO.
Sure. I'm not looking at collecting Macross and Robotech toys as an investment... simply that if for whatever reason I would ever need to sell them, they'll at least retain most of their value. This is a big plus as these guys can run a pretty price.
I am selling a handful of MPC Robotech toys at a slight profit to supplement my Macross collection.