I was also surprised at how high the maxed out laptops can go in price. From memory, around the 2015 model line the top end would be at around $3000 without the crazy disk options.
There was a rule of the thumb that Apple priced their product at a rough ratio of $2 / day. That would give 4 year for my 2014 laptop, and it mostly did. That would be 5.5 years for the top end 16" laptop, I guess that's reasonable ?