The problem with including the cost of your game into the discussion is that it makes the discussion very one dimensional.
"That game sucks because I got it for $60"
"Weird, I enjoyed it, but then again I got it for $5"
"Oh me too, however, I stole it"
That isn't how you judge a game. You judge it based off of the musical score, the plot, the game play, the number of bugs, the playability. There are so many other criteria to whether a game is bad than whether you feel you got ripped off. And certainly, that type of judging breaks down when you get people who can afford any game versus people who cannot.
I understand this thread is about the worst game you purchased, and I think the "you've ever purchased" is in the title because they don't want everyone to go digging around the internet for the worst game, but wanted personal experiences with really bad games. A personal experience with a really bad game isn't: "Half-Life 2 wasn't really worth $60 dollars". That isn't enjoyable to read. It isn't informative, it isn't fun. This thread gains value when people post about how they bought Leisure Suit Larry 9 because they loved the series only to find out it was complete and utter shit. Or how they received Heretic instead of Hexen for Christmas because their parents didn't know the difference. Or how they got Ultima 10 because the series was hugely popular only to find out the game had more game breaking bugs than just about any other game in history including several that made it impossible to advance in the story without restarting (and that came very late in the game). These are all personal stories from me - I expected you all to have some.
If one person thinks HL2 is bad because it cost $60 and another doesn't think it is bad because it cost $60, then the price of the game is not a good indicator for whether a game is good or bad. It is only a good indicator of value. And value is a whole separate discussion.