Could you explain to me how a DJ is worth that much compared to hitting random or play on a playlist on your MP3 player?

Ask the wife :)

But a DJ is more than the money; they control the tempo/crowd for the other things like garter toss, cake, parent/child dances.

I could ask why a developer in California is soo much more than a developer overseas - and they answer would also be they are kind of a like, but you get what you pay for.