I use 27” 4k monitors with macbook pros running at 5k retina scaled down to 4k and it looks FINE. It doesn’t look as good as 5k, but WAY BETTER than non-retina.

I use 27” 4k monitors with macbook pros running at 5k retina scaled down to 4k and it looks FINE. It doesn’t look as good as 5k, but WAY BETTER than non-retina. For about the third the cost, you get about 2/3 of the benefit.