I knew very little about TM units before I bought them , however I learn fast ,I have seen a few HM invoices for servicing and repairs . I am guessing that they think because the machines can gross high hourly rates they can charge 4x what a briggs dealer will for an engine service.
The fact is any machanical person can and will work on these units if you look carefully enough .
I think it is a massive myth that they are some complex ,mystical machine that only they can charge high prices to buy and own.
They are all essentially a small engine, a pump , blower and heat exchanger , cobbled together in a garage originally (see Hydramaster us site) they are over complicated for what they do , and if people wish to pay for advice on how to fix faults they are free to do so , but in my opinion it is a waste of cash.