All I want is a 35"+ 4k display with a 60hz refresh rate for under $300. Is that so much to ask?
Yes, it is, at least with current manufacturing capabilities. Small high-density screens are exactly that -- small. If you have one defect every 30 cm (linear) on average, this may affect one screen out of five -- and even then, there's still some non-critical use where that screen will be just fine. (The front panel of a radio, for example.)
If you're trying to produce large panels with that same defect rate, your rate of defect-free panels is going to be astonishingly low, and there won't be much of a market for the defective ones. Even if Yamakasi is willing to buy and package them, it hurts the image of 4k in general that they hit the streets at all.
This high failure rate means the panels are going to be expensive, because you're not just paying for the one you get. You're also paying for the ones that didn't make the cut.