Am I getting ripped with maintenance expenses from PM?

I say yes, you are being taken. I've never had to do more with a gas line than replace a valve or dope and tighten a fitting.

A $250 w/heater repair?   To do what?  I've replaced t-stats and heating elements. The kit is $40. I've also replaced one t&p valve. $15.   Not much else to repair on a w/h.  Drain valve maybe but in 20 years with dozens of tanks I've never needed it. 

With labor I could see a lower element or drain valve costing $250 but ask what was specifically done. T-stats take 5 minutes. 

Your PM needs to be more specific  about both 'repairs' and provide you before and after pics.  Do you not have a $300 cap on repairs they can make without your consent? 

These are the real costs of having a PM.  Repairs and fill fees.  Everybody gets hung up on the % of rents. 

My PM tried to mess with me, but I'd go over and square it away myself. 3 days ago I got a $600 quote to replace the leaky irrigation backflow valve and troubleshoot wiring to the timer.  I fixed both in 20 minutes and told the irrigation guy to not come back.  This wasn't a direct quote from the PM so I will keep them for now.