Cheap means different things to different people. I had people give me "cheap" red dots (the $25 kind) and I tossed them in a box about 10 minutes later. But $200 doesn't really seem "cheap" to me.
But beyond the things I mentioned I really don't know what all the differences are. Can you educate us?
This is an excellent question and I'll do my best to fully answer it.
You mentioned build quality and always on, but what do those things mean?
The long battery life is self explanatory. If you're going to use a red dot for self-defense, not having to turn it on when you need it should be a no brainer. This alone would put optics like the TRS-25 out of the running if the gun is for self-defense.
Build quality is a more complicated subject. The most obvious aspect is durability. What material it's made of, how it's constructed and how it's engineered are all part of build quality. Ease of operation is also part of build quality. How easy is it to adjust? When adjusted, how well does it stay?
Then people talk about quality of customer service. Primary Arms, Vortex and Trijicon all have fantastic customer service. I don't know about cheaper brands, but then does it matter? I mean, great customer service is...well...great, but wouldn't it be better if you never needed it? So, I want a device that won't break in the first place.
Ultimately it comes down to how you're gonna use it. If you just want to poke some holes in paper at the range, just about any optic will do. Or will it? When I go to the range, the amount of fun I have is proportional to how much work I have to do. If the gun or optic breaks, I'm not having fun. So, I want an optic that isn't going to break, that won't need to be zeroed every time I go to the range and that was easy to zero in the first place.
Have you ever tried to adjust a scope and felt that the adjustments were not positive? Or that they felt kind of squishy? I have. It's much easier to adjust the optic if the clicks are positive and easy to get to. For example, I had a Vortex Sparc, the windage adjustment slot was shaped so a coin could be used to adjust it. However, it was placed too close to the battery compartment and a coin couldn't be used to adjust it because the coin would hit the battery compartment wall. That's a design flaw. Not horrible, but frustrating.
What this means for me is no TRS-25 or similar optics. I have a Primary Arms Advanced Micro Dot. I've had to send it back once because the windage adjustment quit working. They fixed it without question and I do think it's a decent enough optic, but it's no Trijicon.
I don't know if this dissertation answers your question. I'm just tired of stuff that doesn't work.
The Trijicon RMR is smaller and lighter than the TRS-25, PA Advanced Micro Dot and similar optics. The dual illuminated version requires no batteries. They are beyond tough. They have clear glass. When you absolutely, positively need an optic to work, these will.
The Aimpoint optics are also very tough, easy to operate and reliable. I've used the Comp M3 and it's a really nice optic. I haven't used the T-2 or H-1, but I'm sure they're fantastic as well. These are made in Italy. I admit that being made in the US biases me toward the Trijicon.
Ultimately you'll have to decide for yourself. All of these are a lot of money. Even $90 is nothing to sneeze at. I've done the cheap ones and I'm willing to take the time to save up to get the right one. If that means my wife gives me $25 at my birthday and I save it toward something more expensive, that works for me. In fact, we both do that for stuff we want.