Whether they be "Travellers" or gypsies "roma", it is a poor, and insulting, simile. It is hard to believe a fellow tradesman would be so ready to cast aspersions.
I must of have missed the dimensions of the home in question. Whereas it might be safe to assume the boiler is over-sized (an unfortunately common practice among all HVAC professionals), it is a leap, given the facts, or lack thereof.
Having been a sworn police officer, I am also aware of various confidence games and related fraud. Our industry is not immune to criminal activity but, is certainly not a common perpetrator of such crimes either.
The facts point in the opposite direction. Buy the shear numbers of failed heating/plumbing contractors, it is clear that they do not (as a whole) overcharge by habit, training or innate criminal intent. No, more likely, they oversize
equipment out of innocent ignorance. Since the cost of the boiler itself is a mere fraction of the cost of a working system (what you actually need and pay for) the size of the boiler, is the most important aspect in terms of
performance and much less a factor in terms of cost. I have in fact lost jobs because mine was the only properly sized boiler (following a proper heat load). As is evident in this thread, the facts are turned against the informed.
The guy with the biggest boiler (not the biggest price) should be scrutinized.
The bulk of my business, here in Minneapolis, is condensing boiler retrofits (Weil McLain Ultas included) and the cost of replacing an old cast iron boiler and conventional water heater with a high efficiency condensing boiler and
indirect water heater, will often run in the range you describe if installed by a professional, licensed, competent contractor.
It is always good practice to solicit three proposals before buying a new boiler or furnace. A deposit is not unusual but full payment in advance is.
Unfortunately, what passes for "research" as is pertains to condensing boilers if of little value by any standard. Boiler systems represent a very small (less than 2% of the US residential heating market and thus makes for a somewhat
esoteric subject with little evidence and even less expertise from which to draw. Suffice it to say, that we often spend thousand so dollars re-piping failed or poorly performing condensing boiler based systems every week. If your father's
Weil McLain Ultra and indirect were installed to factory specs. in a safe and professional manner he was not swindled but perhaps could use more attention as all have attested.
As an aside, I would not have much luck reviewing my 84 year old father's expenditures, more especially after the fact.
Best of luck.