It's not conjecture, it's fact...if you drive the car things wear out and hard parts are not inexpensive, particularly when labor charges are figured in. If your experience is that your cars never need repair, then that is your experience. I assure you, though, that such a claim is the exception, not the rule.
Until recently my commute was 3k miles per month. Even though mostly highway, things add up and wear out. I have only owned a 123 diesel, but I know from my own experience and the experience of others that $1500 per year in maintenance is not out of line at all. Have you had to buy a trans for either of your coupes? If not, then you have dodged a bullet. If you have, then spread that cost over the miles driven and you'll see what I'm talking about. Have you had to pay the numerous hours of labor to replace leaky auto trans hoses on your cars?...same story. Rear axles replaced?...priced a starter lately?...you get the idea. Am I complaining?...no, in fact I'm shopping for a DTD right now to replace our sedan. Am I telling the truth about my experience (with a 343k mile car) and the similar experience of others?...you bet.
If this were not the case, then there would not be the same urgency to have documented service records and competent PPIs performed. The FACT is that these are unusually sturdy cars that will last for a *very* long time if properly maintained, and that maintenance is not cheap. Parts prices are only part of the story and I use MB or OEM as well. Flat rate for good indy shops where I live ranges from $60-70/hour, and it adds up even for simple repairs. Conjecture?...not in this case.
'76 Moto Guzzi 850 Le Mans