Most optics comapnies have thier own coatings that they developed. I bleieve Zeiss was the first in the 40's with a magnesium flouride coating that let more light through the glass instead of reflecting it off. Swarovski's is called Swarobright. Sightrons if Rev Coat. The more coatings the more light is allowed through the glass. And also the more expensive it is. And it is worth every penny. The beast scopes have just about reached the theoretical limit for light transfer nowadays.
The better scopes have more forgiving and longer eye relief. This is really important esp if you wear glasses or have a really heavey recoiling rifle.
The precision and repeatability of the scope adjustments is crucial. Some cheaper scopes lack precision. If you zero a cheap scope at 3 power, then crank it up to 9 power, the point of impact may wander. Also the adjustment clicks are supposed to be 1/4" but may not be on cheaper scopes.
Some cheap scopes aren't as water tight as some better ones.
Cheap scopes often do not handle recoil as well as better ones. This means that with repeated shooting, the point of impact can wander, the reticle can shift, glass can fall out, watertightness can be affected, etc.
In my opinion, the beat cheap scope is the Bushnell Banner scope. About 70 bucks or so. But it is not fully multicoated. Still for 70 bucks you can hardly go wrong.
Bushnell, Burris, Sightron, Simmons, weaver, Nikon, Pentax, and Leupold all make decent (and sometimes excellent) scopes for under 200 bucks. Probably the best deal is the Burris Fullfield II 3-9x40 which can be had on ebay new for 150 bucks or so. It is fully multi coated, lifetime guaranteed, and enjoys and excellent rep for image quality, durability, precision, and customer service.
I believe it is better to skimp on the rifle and spend more on the scope. You can go get a 50 dollor scope but you will just end up moving up in quality, either in increments or all at once.
Generally European scopes are the best, Followed by US and Japanese, then Korean, Then Chinese. Most Chinese scopes are crap but the new Simmons master series is pretty good.
Leupold is by far the most popular scope for U.S. hunters and for good reason.
There is a company called CDNN that is selling the Smith and Wesson Scopes and the Redfield 5 star scope (both Japanese) for 100 bucks. These are great scopes for the money. I have a smith and wesson.Send me a personal message if you want the web adress of CDNN
Good luck