You don't buy high PPI displays for additional screen real estate. You buy them for the same screen real estate with much sharper, crisper text rendering.
You should always assume that you'll be scaling your image at 2x when using high ppi displays. Take the iMac 5K for example - it offers the same screen real estate as a 2560x1440 display, just twice as sharp at 220 PPI.
You should always assume that you'll be scaling your image at 2x when using high ppi displays. Take the iMac 5K for example - it offers the same screen real estate as a 2560x1440 display, just twice as sharp at 220 PPI.