With Google Analytics I can see how many time a particular ad has caused someone to go to my website. I have tested the same add with and without pricing, and the ads with pricing create more referrals to my website.
I have my own opinions about why it works but I don't have the same statistics to back it up. We live in fast pace environment and people want answer immediately. I know that if I don't close a client the first time I talk to them the chances of me getting their business are at least 50% lower.
I have returned voicemails 10-15 minutes later and they have already found someone else, that is a weekly occurrence.
Everybody has different business plans, so what works for one doesn't work for the other. I wish we all took more of a coaching role to help people with their questions, rather than some of the posts I see.