I just packed up my movie block collection, because I am moving soon. However, it may be some time before these cards see the light of day again, because I am starting at a new job and I will most likely not play them for a long while.
I would never consider selling them though. I would never get the money back again and it is, simply put, good to know that they are there. It would be too much trouble building such a collection again.
If you REALLY need money quickly and you have no other means, then it is OK to sell cards. Otherwise, stop smoking, drink less, go on a diet, or something along those lines. You would be amazed how much you can save by cutting down on your everyday-spending.