one reason they are so much more expensive is because they are IPS/S-IPS panels instead of cheaper TN panels
What about 1440p IPSs or 1200p IPSs, they cost 3x-5x less
16:9 is the standard so it is in high demand, meaning more are made so they cost less. 1200p monitors are 23-24" so they also cost less than their 27"+ counterparts. 1600p is a super-niche resolution at a larger screen size, so far fewer panels are ordered which drives up the price of every unit.
I'm happy with my 24" 1200p IPS but if you really want 1600p you're going to be paying for it big time.
You could always just buy three 1080p monitors and turn them vertical. ;-)