I was looking at pricing for Regent yesterday and their pricing is complicated but you do get one benefit.
I admit I like having everything arranged by the cruise line - it means they always know where I am. If I book a separate hotel after a Silversea or Seabourn cruise they don't know where I am, but with Regent I am still "on my cruise" if you will.
It's one point of contact for the entire trip. If my flight is late they will know it, if my tour is late, same thing. It does make for a worry-free vacation - as long as I am willing to pay the price:
I saw a "brochure fare" of $30,000 - but that was then reduced to $15,000, then there was a "special offer discount" of $5000 per couple, so this made the price $12,500 per person for an 18-day cruise.
Well, this is still sounds pretty expensive, until you see it includes a pre-cruise hotel, and post cruise hotel, airfare(!), shore excursions, blahdy blahdy blah...
I am now going to compare this to Seabourn and see what I get - but convenience does have a certain amount of value.