If you ask me which is the best way to drive traffic I will answer you PPC.Last time I didn't use it very well.Finally now I have master the skill of PPC.Each time I deposit $60 into PPC,I will earn $600 from clickbank.
PPC is very profitable IF you can find something that converts well for you. Don't forget to mention that
How much time is it taking you to get that ROI? I agree with everyone else - If you can, and if your market can bear it, definitely take that income and reinvest it back into the same campaign that's making you that $$$. I'd milk it for all that it's worth.