Get a few more quotations. We have a relatively straightforward vacation house in Western Ma, and we were quoted anywhere from $8-22k for a 2 to 4 split on a ~1200sf house. This was 10-18k btu. The latter of which is absurdly overkill.

But I think in Berkshire county these things might actually be a little more expensive, because there are fewer people who do them out this way.