Precisely, the cost for a pair of bifocals varies the option you choose such as what kind of lenses, coatings, lens materials or frame materials you choose. Moreover, the price of bifocals vastly varies from online eyeglasses shop to optometrist's office. You can cost around $100 to buy a pair at online eyeglasses store, or you also can cost more depending on your prescription whether it is strong or not. Here is my suggestion, you can load on an online store and choose a pair according to your prescription and then you can compare it with that in your optometrist's office and then make your decision where to buy yours. Hope this helpful.