There is one thing that is forgotten on this discussion, that is the warranty.
If you do the repair yourself, and the engine fails at second flight, you cannot complain, but if the engine has been serviced by a company, you will expect that the engine be rebuilt for free if the failure has been caused by improper assembly.
Repairs aren't a profitable business. Don't know all manufacturers but at JetsMunt, labor is always a flat rate of 60EUR for repairs that don't need full disassembly, and a flat rate of 150EUR for all other repairs. Total is these 150EUR + the parts replaced. These 150EUR (190USD) pay for the labor, the premises, balancer, tools, training... but also pay for the warranty that legally should be given for all repairs, at least here in Europe.
Gaspar