a ppc that is worth it

I started am looking for a new pay-per-click program to promote my website. I still try to work with Google and Yahoo, but though the amount and the quality of clicks is decent, I feel the proportions of the money spent on ppc and the money earned though it is not in my favor.

Has anyone tried a cheaper option that would bring adequate results? I wanted an opinion from someone who has tried it, because the description of what they offer doesn't always quite match the reality I have to face.

Any suggestions?

The only other PPC engine I've had any success with is Lycos AdBuyer. The volume isn't even close to what you'll get from Google/Overture, but with the combinantion of decent conversions and lower CPC's I was able to make a profit from the campaign.

We are happy with Trevolta. The quality of traffic is good and it is not ax expensive as Google for us.