Charge a higher service call rate, you should make at least a little profit if they decide not to repair. Sell harder, $175 is not a bad price. You're not just selling the repair, you're also selling convenience. If they buy the used stove, they'll have to either haul it themselves or pay someone to do it. Can they hook up the gas and not have it leak? And then, they will have to figure out what to do with their old stove.