My eyesight used to be excellent, well above average as a young man. Since my late 40s it has deteriorated quite markedly, both farsightedness and astigmatism having reared their dual heads. I can drive a car without glasses, and read without my cheaters in outdoor light, but I can't shoot very well anymore with normal open rifle sights -- the front sight won't properly focus without a corrective lens/aperture such as that shown in my avatar at left.
Some telescopic sights present problems for me too. Unless its eyepiece focus has a large enough adjustment range, the reticle doesn't sharply resolve for me.
When I look through an electronic sight, the red dot looks like a nuclear trefoil:
I can still determine the center, but it's hardly optimal.
I recently bought a Primary Arms 1x prism sight with an ACSS reticle that I can just barely focus by positioning the sight very close to my eye and cranking the focus ring all the way in. I like it.
I've also recently been experimenting with a cheap ($100), heavy Monstrum 4x fixed-power compact scope that also features an illuminated ACSS reticle. Rather surprisingly, I can clearly resolve it's reticle very easily within a fairly large eyebox. An optician could probably tell me what's going on here; all that I will say is that a reticle I can clearly resolve is my first priority with any optical sight.
As my eyesight has deteriorated, I've been growing quite fond of older, low-magnification fixed-power telescopic sights. Often the simple post or crosshair reticles resolve quite well with my eyes. The glass and coating quality back in the 1940's-60s doesn't compare to the present state of the art, the W&E adjustment usually isn't as positive and older scopes are notorious for fogging. However, those that have been well-cared for are still a big improvement on iron sights. Plus they don't cost very much on the used market.
I'm not sure what this has to do with money spent on optics, except that unless eye surgery can improve things I'm inclined to stay near the cheap end of the spectrum.