Dick, I'm totally with you on this, judging from your humble roots you obviously know the true value of money, especially as you have been in the electronics repair business!
Having flown this type exclusively for some years I soon become aware of the horrendous expense of the A109 display units. The replacement prices are unreasonable and eye-watering. We've had a number of them go wrong and all I can say is, I'm glad I don't have to pay the bill but sympathise with those that do.
As I understand it, the displays are a type that is exclusively modified for use in the 109 series and there is only one company authorised to supply and repair them, as has already been stated.