It's not the frames though Aggers, it's the lenses and extras - and the extras are often essential. Although the more expensive frames do usually look and feel more robust.
I have varifocals, and couldn't possibly buy a pair of reading glasses off the shelf because my eyes are so different. But then the pair I have for sitting here, prescription-made to the exact distance I wanted, for reading the pc screen, was only £20 for the frames and I think another £20 for the lenses.
The varifocals also have transition lenses, living here when the sun's out it's very bright especially by the sea, so to have just one pair is far easier.
Then the left eye is very weak so the lens would be much much thicker than the right, so I pay to have them as thin as possible.
And once you're spending that much on them you want them scratch-proof as well
I appreciate about the measuring too, the varifocals arrive with little marks all over them. And I have a small head, so things like the length between eye and ear always has to be adjusted. I must have tried on about 30 frames before choosing, and it's comfort as much as what they look like, you can't do that online!