All businesses exist to earn profit. Businesses like prescription eyeglass optical shops are very, very profitable. Frames can be sold for a profit of 400% or more specially China made ones. Including coated anti glare lenses that are not really scratch resistant and greenish coatings may flaked off in a year or two. Very expensive branded coated lenses have a warranty card from the manufacturer. The polycarbonate lenses can flex a little but can be easily scratched and if subjected to very high heat/flame, will deform.
Optical shops seldom shut down due to business losses and often last for decades. One or two transactions a day is more than enough to cover operating expenses.
My next business venture is naturally in the opticals/eyeglasses and I expect to earn a million in the second year and millions yearly.