[Signman]

It's real simple:
Sometimes you feel like you received a fair value for your dollar and your business was appreciated then sometimes you don't but continue to work with the company because you invested in them and there are no options.

"I guess it would be better for us to tell you we no longer service your model and you are S.O.L., then again you might complain about being S.O.L.....?"
Just a little condescending.
From your company perspective the only option is to charge double or not service the product at all.
Your strategy to keep a long time customer and convince them trading up is a good option is telling them what they own is no longer any good because it's been in service too long. Why not service the unit and leave the customer with a smile so when the cost to repair is not justified they naturally trade up to your new product because of the good experience and service.

I don't believe "the customer is always right" but the customer should always be serviced in a way that they feel they received value and their business is appreciated.