I think Thumbtack's lead pricing system has worked broadly, without, however, working optimally. One issue is that the pro takes on all the financial responsibility for an interaction. A potential customer can choose to post an idea, without any financial consequence. There is no mechanism to assess or control the seriousness of the idea.
I propose the following two changes:
1. Thumbtack provides the FIRST ever inquiry of a customer account holder to pros for FREE. This gives pros some security in the absence of any information on platform use of a new customer. And it works in the context of point 2, below.
2. Thumbtack monitors the track-record of customers, according to some metrics, and determines lead pricing in part based on the observed seriousness, responsiveness and other observed characteristics of a customer. Customers with inquiries that lead to hires can command higher lead costs. Customers with less productive inquiries can lead to lower ones. Some effort could be made to determine causes of non-productiveness as well.