The prices are going to bounce up and down on the Getaway cards because people will buy and either trade them more for profit or use them. The more people that use them the less it will bounce, the prices will go up because there is no source for them, and when they are used they simply go poof. The normal cards are still obtainable so the prices going high has pretty much no chance.
Here's a typical virtual goods price graph explanation;
Starts very high at the beginning of the event
As the event draws on, people want them less because they're less new, so they curve down until the graph looks fairly level
I'll refer to this point as the "true price" because this is where supply/demand balances out, and it will continue to stay fairly level until the end of the event
Around the last day of the event and up to a week after, prices will jump up again. They won't jump by very much, not nearly as much as they were at the very beginning, but enough. The reason for this is that dunderheads think that because the items won't be available to get, the price is going to skyrocket. These people are wrong, and actually drive the price up because they're increasing the demand dramatically on the last few days of the event.
After that point, nobody is buying cards. All of the dunderheads have stocked up on cards and are waiting for the price to go up, not buying or selling. People who have been trying to sell their stuff get increasingly more anxious about selling their cards because nobody is buying, and because of this price drops.
The price will drop indefinitely, until rock bottom is reached. You should buy at rock bottom.
Rock bottom could occur anytime from 2 weeks after the event to months after. After rock bottom, the prices might slowly start to increase again, but it might take more than a year for the item to reach its "true value" again. Whether the price increases again is a function of the residual physical value of the object, it might just stay at rock bottom forever
If you don't believe me, look at a market graph for a summer card. Or, take example from the dozens of times tf2 promotion items did the same thing.
