How Many?

A trip to Halifax today to collect new glasses.  SpecSavers in Halifax is 9 miles from Maison MD but three sets of serious roadworks and numerous slightly less serious (but still with traffic lights,) together with difficulty parking, resulted in a journey of just under1 hour . It was one of the most frustrating journeys I have had for years.
Whilst waiting for my glasses I sat looking at their display of frames and thought about how many ways/designs there must be for the 'simple' task of putting two pieces of 'glass' in front of your eyes, using a 'frame' that goes across your nose and hooks behnd your ears.............and how they justify the resulting cost ......