Old games. The ut3 new and still worth 50 or a little less. The others probably not selling well enough and can pass as freebie to make likkle more money. After they think the market for a game is saturated they can do whatever.
One thing tho is the price of the orange box which has 3 games in it. Thats a deal... maybe. But considering every game in it came from the same engine etc... maybe they had more room for pricing