So what backs up the steam driven gauges in most aeroplane, the ones with a mean time between failure of 800 hrs?
You mean like the wonderful KI-256 vacuum horizon which will fail; not if but when, and I am not talking about the vacuum pump, either (which will fail even sooner, not if but when)
And this wonderful KI-256 product costs a cool $11,000, or $3,000 as an exchange refurb from the USA.
Glass cockpit planes have conventional gauges too. I think most new glass cockpit pilots tend to fly them on the backup instruments
The new v. old argument will run for ever. I am firmly convinced that for most metal planes, assuming a 15 plus year ownership, the total costs over the ownership period are not very different, with the extra huge bonus that the new one will have spent a lot less time collecting dust in hangars. I bought a brand new TB20GT in 2002 and (apart from the fraught warranty politics etc) have not regretted it for a moment. I'd never do the long trips I do in a plane which has as much downtime as so many I see around the place. The reason the picton GA scene is dominated by old metal is because there is very little capital around, but some of the unscheduled maintenance I hear about is eye watering.
The build quality of a PC12 (I see them regularly, close up) is a world away from "our" el cheapo piston powered spamcans