But you're looking at a very narrow set of products used by developers. What about, say, Aeron chairs?
The point is that developers don't just buy software. They're marketed stuff constantly, like everybody else. To suggest they're immune to it seems a little naive to me.
Same reason a good mattress is worth $1k+.
You spend a lot of time in it, and quality product greatly increases your quality of life (back pain etc).
Note: I have no idea if Aeron chairs are good or not.