Whenever people try to compare the differences in costs between types of entertainment, the most pervasive benchmark appears to be to compare the cost to going to a movie. I'm not entirely sure what the reason for this is, but I'm guessing it is probably the de facto "most expensive" type of entertainment that most people can relate to and have access to on a regular basis. Going to a movie near where I live costs around AUD9.50 per person. Considering a movie typically provides around 2 hours of entertainment, going to a movie is a cost of roughly AUD4.75 per hour per person - this gives us our benchmark number. So, how does it compare to other forms of entertainment? (It'll become apparent why I'm going into per hour as well as per person soon enough.) One common source of entertainment is reading. So let's say, a typical book like The Da Vinci Code is about AUD9 on Amazon. Measuring reading time is a little tricky, especially since everyone has different reading speeds, but I'd say, typically, you'd probably be able to finish a book in 6-8 hours. I'm going to assume you're not going to read it again, but maybe someone else might read your copy - but let's just keep things simple - most people read their own books; so that puts a book at roughly AUD1.50 per hour per person.
What other pieces of entertainment might you have? What about public television? Youtube? Those things are free to the user, discounting the fact that you might buy things from the ads. However, you might buy DVDs of your favourite television show. In Australia, this tends to come up to around AUD1 per episode. This comes up to around AUD3 per hour per person for a 20 minute show.
There's also video games. I'd say the typical game probably provides anywhere between 6 to 60 hours of single player content. Since it's easier to talk about single player games in terms of cost, perhaps a typical game like Bioshock would suffice. Bioshock is about 20 hours, and would probably cost you AUD60 new. That comes up to around AUD3 per hour too.
Then we have board games. Board games get extremely complicated because there's a very good chance you are playing the game multiple times and with multiple people. As a result, this usually ends up being retrospective analysis after you've played the game. For example, I bought Arkham Horror for AUD80. I've spent 12 hours playing it solo, and probably around 6 hours playing it with two players - so this puts me at around AUD3.33 per hour per person, which sounds pretty decent still.
However, the benchmark is really only useful when you are comparing to make a decision - this is usually a purchase decision, which means weighing up a lot of uncertain options. A movie is usually a fixed amount of entertainment, which may or may not be good, but chances are, you are going to be sitting there the whole two hours. You did after all fork out AUD4.75 per hour already - making it AUD9 per half hour doesn't sound like a great proposition. You might think this line of reasoning doesn't make sense, but you probably do it too, although it's a sunk cost.
Since the time investment isn't as great, it is quite likely that you will just sit out the additional hour or so it costs you. To say the same thing about books, entire seasons of TV shows, video games and board games isn't quite so simple. I don't anyone fancies struggling through 5-20 hours of entertainment they dislike, even if they feel like they need to make up for their sunk costs. It feels like this can be a viable explanation for why $0.99 apps sell so well on the App Store. The sunk cost is only a dollar - slightly over a tenth of the cost of a movie ticket for me - for me to match the movie ticket value for money, I only need to play the game for 12 minutes. For most games, that could be the entire tutorial and set of first stages. There's also the fact that throwing apps away (i.e. deleting them) doesn't produce any visible waste, so you don't feel guilty for buying extras just to try them out.
For the most part, it feels like just some massive rationalisation so that you don't feel bad about making a bad decision; just staving off the feeling of buyer's remorse. It's still going to feel like a shame when you buy Arkham Horror only to play it once. Can you really justify spending AUD80 on 4 hours of poor entertainment for 4 people over spending it to have a home movie marathon with food?