What's a Fair Markup for Handling Maintenance?

[Drew Sygit]

So, you hire a Property Management Company (PMC) to manage your rental property(s). 

What are you experiencing or expecting them to charge you for their time spent managing maintenance issues?

In our experience, the cost most PMC's charge for this really isn't transparent because it's included in either:

1) Their hourly charge for maintenance

2) The invoices they send from their company or a maintenance subsidiary.

If a PMC was to share with an owner their true cost, what would an owner feel is a fair markup for handling maintenance issues?