How much should it cost to install a tankless combi boiler?

I live in the Northeast, and I want to have a condensing tankless combi boiler installed to replace my conventional combi boiler. The gas, water, and electrical lines all run to the installation site, and the vent location is about 6 feet away. I am getting quotes for the total install for $7k to $8k, which I think is insane. What is a reasonable price for such a job?