Proof and Mint sets

Proof and Mint sets are like any other coin in the sense that some are more rare than others.  One of the problems with the proof and mint sets, is they take up a lot of space.  The mint does a nice job of presentation, with nice boxes and protective plastic around the coins, but they are bulky.  People get caught up in wanting one for every year, and they get put on automatic reorders by the mint.  When they die, family members get big boxes full of mint and proof sets, and ultimately want to get rid of the coins.
As far as value goes, any set that is made with silver is going to be more valuable than a set that doesn't.  The early sets in the 1930's and 40's can be quite valuable.  As with any coin, it's good to get professional advise when trying to determine if you have something that might be rare.  Most of the common date non-silver sets are going to valued slightly above their face amount.  Part of the reason for this is supply and demand.  There is an abundance of those sets, and not a lot of people are buying proof and mint sets.