My parents had a newer boiler than mine. When they had a gas valve replaced, it cost nearly $500. I called a different HVAC company and they said that it was about right. I am trying assess the wisdom of buying a new boiler. I have an old Maclean-Weil (hope that's right) about 40 years old for a split level home about 1800 square feet plus sub-basement.
Yes, more parts and some are electronic which are pricey. Gas valves are pricey but that sounds a bit high to me by at least $100 for only a valve. Maybe that included a servicing too. Generally I doubt the higher efficiency for a gas boiler will pay off all that much. I usually tend towards saying if it is working then leave it. If it was much older than your 40 years it might be worth it. I would guess you are closer to 80% efficient at that age, that generation of units. Older ones can be 60%-65%. To get to 90+ they add a lot of stuff that cost more, like a draft inducer fans and sensors for it and intermittent ignition. They do require more service. Then you only gain like 10% or 15% max. for the investment. But payoff time is directly proportional to the cost of the gas. Unless you intend to stay in the house for many many years it probably won't pay off. And investing the money from the purchase cost would generate enough income to cover the cost of the slightly lower efficiency, imo. Good Luck.
