Ultimate Hubber has it right -- it depends on a heck of a lot of factors, and one of the biggest ones is what you write and your ability to get the word out to the right market that will actually result in clicks and sales. There are a couple of people here who have single hubs that rake in $100 per day, while there are doubtless thousands of hubs that don't make anything at all either through lack of demand, bad SEO, or bad market targeting. Yes, there is a ton to learn :).
I'm working on getting about 20 of my SEO articles on here, and will eventually be getting some hubs up about some very effective marketing concepts that I've used for myself and for clients. Feel free to check back, or request a hub on a specific question, and I would love to write one for you :).