I don't quite agree re the spares prices.
The reality is that all airframe parts from anyone are silly-priced. £200 for a tiny little 20mm piece of aluminium with 2 holes in it - which the mfg extrudes in 10m lengths for £20/length and then drills 2 holes in it and being a JAR145 firm with the type certificate, generates the documentation from fresh air
That is why one should not buy a really old plane - lots of airframe parts may be needed.
Socata's pricing is not helped by some stupid decisions like ISO hose fittings which result in some hoses costing £200 (£400 from Socata) when a US-fitting hose would have cost £60 (Teflon, etc). But one rarely needs these (engine overhaul time only, and Teflon hoses have no life limit on the TB).
A more general issue is a lack of crashed TBs from which parts can be transferred. Not a problem with Cessna or Piper.
IMHO, the biggest problem Socata has is that they are French. They have awfully arrogant attitudes and their working practices would have been envied by Arthur Scargill. Only the TBM is expensive enough to absorb the way they "work".
The parts are available 99% of the time off the shelf but finding a decent dealer has at times been very hard. Air Touring had been at war with Socata for years (over warranty reimbursement, etc) before they went bust, and now AT Germany has gone bust too. A lot of people currently buy from Troyes in France who are very good but they keep little stock; they seem to buy back to back mostly (which is quite common for dealers anyway).