@Astro14 would know. He has some experience with them.
Thank you. I would say that my experience with Mercedes has been in two broad categories; My W123 and W124 sedans that were durable, reliable, and inexpensive to operate, and support your point, or my W220 and R230 V-12 twin turbos that have been fairly expensive to maintain. The latter two are the opposite of what's being suggested. They aren't cheap to own, but they have been reliable.
They're indulgences. Wonderful cars with breathtaking performance and smoothness.
If you'll permit me to put Volvo in the luxury car class, then, yes, an older, well-maintained luxury car can be an inexpensive, reliable daily driver. The 5 Volvos in my sig are driven daily by 5 family members. I'm driving my V70R in Denver today.
They range from 19 to 22 years old. They have just over a million miles on the group (range is from 125K on the low side to 295K on the high side). Number of times they have, as a group, left someone stranded - once.
When my wife had a cam seal blow out in her 2002 V70XC, due to a failed PCV system (that had been fixed, though not completely, by our dealer). She pulled over when she saw the smoke trail. We flat-bedded the car home, and I dropped the oil pan to fix it. I am now much more careful with PCV system repairs. That was over 10 years ago, the car hasn't had any major issues since, though it has had a complete suspension rebuild.
So, there you go, a fleet of 5 "luxury" cars, a million miles of aggregate experience, great reliability.
We can add a very low total cost of ownership. Let's take the middle car, my daughter's 2002 V70 T5. Bought in 2007 with 72,000 miles on it for $12,500, cash. On the road 16 years later, with 225,000 on it, in daily service. Insurance is low. Depreciation is very, very low, on the order of $600/year. Repair cost has been modest.
A good car, well-cared for, even if a "luxury" make, can be a very inexpensive option to own.