Can I point out that Bangor is in the United States, and the MRO in question has a long standing relationship with Loganair over many years.
Your estimate of $150k for a standard 'C' check is way off he mark given the age of the tails involved, I've had 20 odd years experience with them.
Loganair want a decent product in return, sadly some of the European MRO's quality is falling far short of the mark.