I have the mibox S, I can watch Netflix in 4k, costs around $65

I have both. But besides these options you are probably overwhelmed by the selection. It's easy to narrow it down, you want netflix, Hulu, and Amazon prime, right? Netflx only licenses this to about 6 devices total. This Site reviews them all and lists app support, along with 4k. It will make your decision much easier. The shield will probably get updates for a lot longer but the miibox is just fine!

Go with shield.

You can look at Xiaomi boxes, they are cheaper do 4k.

I know it's another tier of expensive, but if you go for the Shield TV you will not regret it. It is a significantly better product with outstanding support behind it (this is critical as Android TV evolves fast and many other boxes quickly become abandonware).

There's really only two options that run the Android TV operating system and are readily available: Shield and Mi Box.

I'm worried that if you're browsing Amazon, you might be coming across several products that use the phrase "Android TV Box" which is just a TV Box that runs Android and not a Box that runs Android TV. The former is not recommended here, and the latter is the exact topic of this subreddit. A lot of Chinese junkboxes are just hacked together using old versions of a touchscreen OS and they offer zero customer support. You don't want old software. You don't want a touchscreen OS for a living room television. You want support if something is wonky or breaks.

If you're going to consider Amazon's line of Fire TV products, those are a fork from Android in a similar fashion to how Android TV is a fork from Android. Android TV was forked by Google and designed to work on devices like the Nexus Player, Shield TV, Mi Box, etc. and Fire OS was forked by Amazon for their products. So for Amazon, it's probably better to ask a related sub for more input on their line of products instead of this subreddit. Some people here have experience with both sides though. I've only ever had the cheap 1st-gen Fire Stick and that thing was slow garbage. It was about as good of a UI experience as an old smart TV. That's not good. I eventually just got a Shield and have been very happy with it. The best tech purchase I've ever made! I'm sure the newer Amazon devices have made improvements in performance though.

If you want Amazon Prime access, I think you're kinda stuck with getting a Shield or an Amazon box. I don't believe the Mi Box has access to that service. You might have to sideload the Prime app or do a more complex workaround. Someone else may chime in here with the best solution for that. (I've never used a Mi Box myself)

Personally, I highly recommend the Shield all day long. It's worth every penny.

Amazon fire stick 4k is dead simple easy to use and was cheap. I enjoyed my mibox but did have issues with it. Got amazon fire sticks christmas of last year and were golden. I just wanted tv though not any web browsers or such. Ymmv

These are the legit Android TV devices that will have DRM for streaming of copy protected, paid for content.

Be aware not all devices have Netflix approval:

https://www.reddit.com/r/AndroidTV/comments/cguehm/androidtv_device_comparison_table/

Not all devices come with the Amazon Prime App either. Some cannot do 4K HDR YouTube.

It's a minefield, so you really have to list EXACTLY what mainstream Apps are required.

Also be aware Apps that are coded for the mobile/tablet version of Android that are sideloaded into Android TV devices will often need a seperate air mouse to use them properly like a WeChip G20 or a MINIX A2 lite remote

There are other App control difficulties then as well, plus screen orientation issues.

Money no option - Shield

Mid range price - Formuler Z8

Low price - Firestick 4K