This also jumped out at me. My company (http://www.firebox.com) is built on having amazing looking images for products. No one could see any difference between the quality of images between 87 and 95, but it saved us roughly 50% in file size. Also for what it's worth, we spent a lot of time a/b testing 87 vs 95 with our users, but there was no conclusive difference
We use GraphicsMagick at 92, as dipping into the 80s has an annoying tendancy to introduce visible noise on something like 1:50 images. It's very annoying to ship that extra bandwidth.
Interestingly, we've done WebP support, and while the files are smaller across the board, visual quality deteriorates really quickly once you start dropping that quality value, even in small increments.
