Mr Fixit
When I worked for Air Canada from 1998 to 2003, we did America West Airlines (AWA) heavy maintenance on their A320's. At that time, AWA had 16 different MRO's doing heavy maintenance on their fleet of aircraft. The FAA advised them to reduce that number significantly, to a manageable figure. We also did JetBlue, Skyservice and Air Jamaica A319/320/321's. The fact is airlines can make a healthy buck by doing third party maintenance, whilst outsourcing their own.
Air Canada used to charge AWA more than USD$75 per man hour for maintenance at that time and pay us around CAD$35 - $40 per hr (top rate). It adds up pretty quick when you calculate that on an average of 30,000 man hrs for an A320 D Check. All airlines are doing tha same, as is evident in your post.
Its sad really.