Sorry I can not help you because I am also new here, just began to arrange to get my Amalgams removed. I just wanted to say that $5000 for four Amalgams seems a lot. Is it because some of them need to be replaced by crowns?
I will have six Amalgam removed, one small and the rest medium sized, and the total cost is $1921 (I'm in Seattle). Each Amalgam replacement costs 200-500 depending on how many surfaces there are.
Before I decided to go with my current dentist, I also did a free consultation with another mercury-free dentist in my area. At the time, he didn't give me a quote, but he told me that one of my Amalgam tooth probably needs to be secured with a crown because the filling is pressing on it. A crown is usually $1200-$1400. However, when I saw my current dentist, he didn't mention a thing about the need of a crown. I even asked him if my fillings were too large and if they would press and break my teeth during the removal, and he said no.
So I think it's wise to get a couple opinions from different quality dentists because they could differ a lot, some might save you from over dental work and make the experience more comfortable also.