"I often wonder, in general, when one buys an expensive esoteric audio product, does one typically get comprehensive and extended service included with the purchase? Or do the service bills reflect the cost of the product bought bringing up the TCO?"
I have found dealers to be helpful on out of warranty problems in the past on very expensive equipment (Levinson), but you can't count on it. Many high-end dealers also offer very favorable trade-up policies (sometimes full original value, if you trade up by a lot), and trade-up policies are often more valuable than service policies.
For speakers the service problem is espcially acute, because very expensive speakers are usually huge and heavy, and a PITA to ship.
I've found high-end OEMs are not afraid to charge a small fortune for service. Electronics are the worst. Most problems can only be solved by board-swapping, and often a new board will cost thousands.
High-end audio is like high-end cars. You can get them used cheaply, but if they break they are still high-end products and they cost a lot to fix.