I would say 250-260MB/s for a 16TB drive, and when 4TB drives were newer they were more like 160-180MB/s. That's about a 50% increase.

Doing the math, you're probably going from 5 to 8-9 platters, so 2.2-2.5 areal density, and a naive square root suggests it should be about 50% faster. So maybe track width is taking a fair share after all?

Though when I look at more sizes, it seems like 12TB drives were also hitting 260MB/s and speed has almost entirely stalled since, with 24TB being only a hair faster.