The title is a bit misleading but it doesn't sound like karma can actually be converted to real money.

Reddit gold is going to cost $2 to buy and awarding a user can give them $1 of that if they have over 5,000 karma. Between 100 and 4,999 it's $0.90 per gold.

And you have to receive at least 10 gold in a month to be eligible. Edit: it apparently rolls over.

Fuck /u/spez