The telescope was invented in the early 1600s and by the 18th-century optical devices were being produced for many different purposes.
The popularity of the theatre and opera led to the creation of decorative glasses.
In the 18th century the monocular or spyglass, predominated, followed in the 19th century by the paired monoculars which evolved into the opera glasses as we know them today, they were developed in Paris in the 1820s.
The difference between opera glasses and binoculars is both strength and declaration.
Opera glasses really magnify more than four times but binoculars can magnify it times and more.
Binoculars are designed to be practical and durable, where opera glasses were function accessory and could be beautifully decorated.
Price depends on materials and condition, whether or not they have the original case as this can enhance interest and also suggest that the instruments have been well looked after.
I strongly recommend some research and seek as much provenance as possible.
I hope you have found this page on Opera Glasses to be both informative and helpful.