Unless you think they undercharged for the amount of content that was in the original game. I'm sure a lot of people feel Fallout 3 had way more than $60 worth of content. In fact, I can pretty much guarentee a lot of people think that because there are a lot of people who think the DLC was well worth the price.
Seriously, we're talking about putting a value on something as abstract as how much fun can be had in a game. Since you really can't quantify the amount of fun and content in a game, it's value can only be based on perception.