Hi, I am Barney, one of the top three commercial photographers on this website, and I have previous undertaken jobs shooting glasses and sunglasses for an American client (250 pairs), and for a British startup client's business launch ... 2000 pairs over five very long days (and the help of a very willing assistant). You can see samples in my portfolio attached to my profile. This job is somewhat smaller but still needs concentration.
Assuming 50 pairs, this is 200 images - straight on from the front, one side, one at 45 degrees, and one at 45 degrees from the rear - and is less than a day's work. The fee quoted assumes white background photography to Amazon's strict standards. All images are edited to remove accidental reflections.
If you want these shot on models their fees will need to be added to the quote, and my time might need to be extended.
Please contact me to discuss full details. Best time is usually between 0730 and 0900 GMT (but not this coming Monday as I have an early start).
Looking forward to speaking to you without obligation.