$250 in 2016 would be $335 today. A 16 GB 9060 costs $370 which is only 10% higher. So prices are getting reasonable; after having been completely outrageous the past few years.
Now these are US prices. But the 9060 is available in Sweden for $435 eqv. which is really not bad.
4K is an outrageously high resolution.
If I was conspiratorial I would say that 4K was normalized as the next step above 1440p in order to create a demand for many generations of new graphics cards. Because it was introduced long before there was hardware able to use it without serious compromises. (I don't actually think it's a conspiracy though.)
For comparison, 1440p has 78% more pixels than 1080p. That's quite a jump in pixel density and required performance.
4K has 125% more pixels than 1440p (300% more than 1080p). The step up is massive, and the additional performance required is as well.
Now there is a resolution that we are missing in between them. 3200x1800 is the natural next step above 1440p*. At 56% more pixels it would be a nice improvement, without an outrageous jump in performance. But it doesn't exist outside of a few laptops for some reason.
*All these resolutions are multiples of 640x360. 720p is 2x, 1080p is 3x, 1440p is 4x, and 4K is 6x. 1800p is the missing 5x.