Wahahaha. Add it to the list, eh?
Anyway, you two sound like a reactionary pair of old farts. Which, frankly, is normally my role.
The price difference is rather silly, but no sillier really than charging $20k more for a platinum watch than a gold one. It's just a differentiation to make it inherently more exclusive, and reflect the small production numbers and handwork. But. It's still an extreme difference, granted. $160k would be a fair budget for a whole collection in my mind!
However, I don't dislike it. The only thing I dislike is the silly deployant clasp. Reminds me of an old time sweet shop sign, and feels so contrived, when the original was already so nice. But overall, I like all that engraving. It's just a different flavour, like gold versus steel, or a croc strap versus a bracelet. OK, an expensive flavour. I like the 5059 too. But if one had, say, three PP perpetual calendars already, you know, like a real crazy PP baller, then the 5160 would certainly be a way to add a different kick to the collection. Then again, depending what the first three were, so would the 5159. Maybe both? :)