Sorry, I haven't bought eyeglasses at specsavers. But if you prepare about $80, I think most types of eyeglasses can be chosen by you. However, about the exact price of your favored type of eyeglasses, you'd better call the store and ask from the client there. This is most easy way for you to know the price there.
I never bought eyeglasses at specsavers. In fact, i never bought eyeglasses from online shop. But to help you. I just search specsavers and find that most of their eyeglasses frames are sold $25. But i don't know how much they will charge for their lenses. So, you may prepare about 100 dollars ( I think you may get a pair about $50, anyway, you can prepare more money for any in cases. Hope this help.
Have you ever visit the official website of Specsavers? The address is https://www.specsavers.co.uk/glasses/
There are a lot of kinds of glasses and contacts that you can see online
the prices can range from 25 to 169 pounds.
And according to the website, you also can find the nearest store of specsavers where you can buy the glasses.