Lead generation pricing model

Hi,

I have recently been looking at providing local lead generation services but im struggling to nail down a structured pricing model.

At the moment i am selling leads to a local plumber based on 20% of the completed sale but im running into a few problems. First of all, because they have nothing to lose if they tend to not treat the leads with urgency unless they are desperatley looking for work. Also if they feel as if the job is not worth their time after the 20% kickback, they quote really high therefore stopping them from getting the job. Its basically quite a bit of hassle at the moment.

Now i have heard of people just selling the leads based on a fixed price but im not quite sure on what kind of commision they are basing it on or charging for leads, plus what is the best way to make it work for forwarded telephone calls. I was thinking i could base calls on "any calls over 30 seconds = a lead" but because they number comes on their mobile they can just cancel the call and call them right back.

Hopefully people have a good structure in place that allows them to pass on leads knowing that they are getting converted at a decent rate and frees them to look for more clients and work on the online stuff.

Cheers in advanced