I literally stated that they don’t have significant control over the lens prices. Every optometrist is getting their lens from a relatively minor set of manufacturers, and the manufacturers price to maximize their revenue, not the optometrist.
Now I’m sure that they make a bit more money in an absolute sense from coatings, but nothing like the full $8 or whatever it costs these days.
The biggest markup items they have are the frames, as there are many different manufacturers the frame manufacturers do have to offer margins to the places that sell them.