Cost varies with the contractor's overhead, the quality of the job, the
size of the boiler, the efficiency of the boiler, the quality of the
boiler, additional piping required, comfort improvements like zoning,
It is like asking: I am buying a new car, how much should it cost?
Even within the same model, with options, the price can vayr
Get several bids.
BTW, the contractor should do a load calculation to determine the
proper size if it is a hot water boiler. If it is a steam boiler, it
should be sized to supply the connected radiation.