Sure, to a point. But the step-up in question here (1080p to 4K, at sizes like 15–27″) has
clearly visible benefits.
And sure, resolution isn’t free, but at these levels that was an argument for the hardware of eight years ago, not the hardware of today. All modern hardware can cope with at least one 4K display with perfect equanimity. Excluding games (which you can continue to run at the lower resolutions if necessary), almost no software will be measurably affected in latency or frame rate by being bumped from 1080p to 4K. Graphics memory requirements will be increased to as much as 4×, but that’s typically not a problem.