[edit] Info from comments demonstrates these results, though simplified, to be incredibly optimistic. Assuming a CPM of $1.00 and taking into account the ratio of paid advertisement to Reddit advertisement, the Monthly Revenue number would dip significantly to $100,000.
It seems that CPMs are more in the $0.50-1.00 range[1]. Which still translates into a very nice chunk of change and that's not counting other initiatives such as reddit gold.
I have no idea but judging from the amount of real ads I see on Reddit, I'd guess they make way more money from Gold than from display ads at the moment.
Keep in mind 90% of the ads right now are just games or reddit ads (keep refreshing the page). Not mention a good percentage of their users use adblock and are extemely anti-commercial. I think they are making significantly, significantly less.
