Remember the last time you bought a full-priced CD from a music store - the kind that set you back $18.99 for 4.5 minutes of top 40 single and 67.5 minutes of underwhelming filler?

Of course you do.

Many point to this as the reason the music industry is in trouble. I say that even at 99 cents for a 4 minute song from the iTunes Music store, the music industry has a bit of explaining to do.

Unfortunately, we're going to need to do a little math.

Don't think of a CD as a collection of tracks pressed between wafers of plastic. Instead think of a CD as 72 minutes of original entertainment. And with a suggested retail price of just under 20 bucks it works out to about 26 cents per minute for those good times. Assuming the average length of a song is 4 minutes, what seemed like a good idea from Apple is actually on parity with full retail pricing at just under a quarter a minute.

So are DVDs a better value? Yes, either by a bit or a whole lot depending on which parts of the DVD you consider entertainment.

Figure $20 for the DVD and 100 minutes for the average movie yielding a cost per entertainment minute of 20 cents. If you're the kind of person who is into the extras, watches the movie again with the commentary, watch the deleted scenes, marvel at the making-of documentary, and watch the original theatrical trailer (which must be one of the most shameful ways to spend 2 minutes of you life) you wind up with something like 3 extra hours of entertainments. Allegedly, at least. This brings your price per entertainment minute down to about 6 cents. Not too shabby!

But none of these can hold a candle the obscene entertainment value of Elder Scrolls IV: Oblivion. I just wrapped up getting all 1000 achievement points which, arguably, marks the conclusion of the game. Reaching this point took me a full 101 hours. Time well spent? Subjective. Good entertainment value? Unquestionably!

The retail price of Elder Scrolls IV: Oblivion is $59.99 for the Xbox 360 version. Do a little math whilst whistling an appropriate tune and you get an entertainment price per minute that could stand up to depression-era economics - a mere penny.

Be careful though. This concept is a dangerous one because very little else on this earth can compete with Elder Scrolls or a good MMO in terms of value. Should you begin to apply the same entertainment value principals to a night out with your mates at the pub, well, let's just say that friends shouldn't let friends do math in their vicinity.