For what they cost, the do pay for themselves after a few cycles. I've heard people pull as much as an ounce off of one of these systems. Pretty good once you consider how much an ounce of good can cost and how many ounces a year you can produce.

General lighting is expected...

24/0 (Seems appropriate for Aerogarden)
18/6 (Mainstream vegetation)
12/12 (General Flowering)

I'm seeing some nice hues of green there.