A Red-Dot type of sight and a "Rifle-Scope" (Meaning variable magnification) are 2 totally different things with different purposes and different levels of quality. The purpose of a red-dot is to replace iron sights and provide faster target acquisition compared to fixed iron type sights. That's it. With the exception of a couple of companies, they are 1X power. The only real quality requirement of a 1X red-dot type of sight, is that it maintain it's zero aim once sighted in. That it doesn't bounce all over the place, or drift because of recoil. If it can do that, then it it perfectly fine for what it's suppose to do. Some people get an orgasm because one red-dot type has a 2moa dot at 100 yards, while another has a 5moa at 100 yards. Red-Dots are open sights. Basically looking through iron sights except easier and faster. They're designed for shooting people with. It means nothing if it has a 2moa instead of a 5moa. As long as the red-dot sight is not all plastic; as long as it holds it's aim; as long as the lenses are clear and you can see through them; then it will work fine. And you can get plenty of red-dot type sights for under $100 that fit this package. If you believe you have to buy an EOTech, Aimpoint, etc... and spend hundreds of dollars, then you are wasting your money. It might make you feel good, and that's fine; but you don't have a better sight because of the price.
Now magnified sights like rifle scopes: 1-4x30, 3-9x42, etc... these are a totally different animal. Besides holding zero, not drifting, construction, and the things looked at similar to the red-dots; the ability to magnify creates a lot of other potential issues. Mainly with focusing. Also; field of view becomes a major issue. Clarity of crosshairs. How much light it can absorb at higher magnifications. There is a totally different quality base when talking about magnified rifle type scope. I have hunting scopes that cost more than some of my rifles.
But when it comes to red-dot, 1x non-magnification, type sights, all I care about is that once I sight it in, that after a few hundred rounds, I don't have to sight it in again. That it's still accurately on target. I care that the red-dot is somewhat crisp. (Hard for someone who wears bifocals). That the red-dot is visible in daylight hours. And that it's not made out of plastic and will break easily. I have a 30mm Tasco that's been on one of my AR's and has been there for about 6-7 years. And I can still hit my 4" grapefruit size area at 100 yards without a tripod or anything fancy. For basically open sights, that is perfectly acceptable for what I want. It cost $32 at walmart. I like the A1optics because it has both red and green. I have that on one of my other AR's. That one does have a 2x magnification. (That's the recommendation I posted earlier). Normally I don't go with magnified red-dots, but I've had a lot of luck with A1optics. So far it's great. That one was $49. I have an Osprey 1x reflex open red-dot. (Not tube/scope type). It sits on my Saiga .223. Just as good as the others, I can shoot my .223 AK47 at 100 yards and continuously hit a 4" center. And this is still basically the same as open sights. No magnification. Just easier sight acquisition. It cost me about $35.
Some may believe that you must spend lots of money on a 1x red-dot type sight. But you don't. Most of the quality issues that scopes have to deal with, come in the clarity, field of view, fogging, crispness of the sight and target, etc... of a magnified sight. A 1x red-dot type sight doesn't have this issue. If the sight is metal (Not plastic). It uses real photo glass type lenses and not some cheap plastic or window pane glass. If it keeps it's zero after sighting in and doing a lot of shooting. And you can easily acquire your target with the red dot. And finally; that the red or green dot can be seen during daylight sunny conditions. Then it's a good sight. And these can definitely be found for under $100. You don't have to spend $150, $200, $300, $500 or more. Remember: These types of sights were to improve on open iron sights. Not to replace or compete with magnified hunting, sniper, etc... type scopes. They aren't for hunting. They're for shooting targets/people at 100 yards.