I offer this as a bit of an FYI: The typical complete set (1 of each miniature) Ebay auction cost trends for a DDM set:

Two weeks prior to release:

~110% - 120% of the cost of buying enough boosters to get an average of 1 of each rare from the set when buying from a competitive online seller (example: ~110% to 120% of the cost of 2 cases of Blood War from Game Outfitter).

At release:

Immediately following release, prices begin to drop.  Within a few days after release, the prices tend to drop to roughly 100% of the cost of buying enough boosters to get an average of 1 of each rare from the set when buying from a competitive online seller (example: ~100% of the cost of 2 cases of Blood War from Game Outfitter).

Two weeks after release:

Within a couple weeks following release, complete set prices tend to drop to drop to roughly 90% of the cost of buying enough boosters to get an average of 1 of each rare from the set when buying from a competitive online seller (example: ~90% of the cost of 2 cases of Blood War from Game Outfitter).  These prices tend to hold for some period of time, but will slowly begin to fall as the set ages.

Roughly 3 months after release:

When the next set is approaching, the set prices for the current set tend to take even more of a dip, falling to roughly 80% of the cost of buying enough boosters to get an average of 1 of each rare from the set when buying from a competitive online seller (example: ~80% of the cost of 2 cases of Blood War from Game Outfitter).  This price tends to hold until the boosters begin to disappear from store shelves.

Product Disappears from Shelves:

As soon as the product disappears from the shelves, the price begins to climb.  The amount and rate of climb differs from set to set.  Some sets only climb a little, and do so slowly.  However, high demand sets tend to rise quickly and significantly, soon exceeding the prices that were observed a few weeks before release.

Please note that these are trends that I have noticed over the past few sets.  There are always Ebay auctions that sell for unreasonably high or low amounts.  Further, trends can change suddenly when a component piece changes - such as increase in the base product MSRP.  There is no guarantee that this trend will hold true for future sets... but it has been true since I've been tracking the price of sets (the GoL era) with only minor deviations.

Note that these numbers apply only to complete sets, not complete sets with extra commons/uncommons.