I know plenty of people who don't make a lot of money (say top 25% or so) that will have a Boat or RV that costs more than a $3500 computer, and balk at the thought of spending that much on a computer. It just depends on where your interests are.
Some people succumb to lifestyle creep or choose it deliberately. Others choose to live below their means when their income grows. The latter have a lot more money to spend on extras, or to save if that's what they prefer.
There are tens of millions of top 10% income adults in America. So something can be both unaffordable to most people, and also easily accessible to very many people.
There are a lot of people who could easily choose to spend $3,500 on a computer.
$3500 is more than I would spend on a hobby too, but there are, in absolute terms, a large number of Americans who can spend this much on their hobbies.
It is easy to confirm this, just look at the sales number of these $3500 devices. It is definitely not an enthusiast price point, even in the US.