Why are Blu Ray's more expensive than DVD's but PS3 and 360 game are same price

[Canada]

The two things that I can think of is that most Blu Rays have advanced audio codecs where PS3 and 360 games have the same audio. Also can some one tell me the difference between mastering a game (if it needs to be done at all) and mastering a movie. The last thing is does it have any thing to do with games being inherently more expensive.