The current 9" and 10" Android headunit price range from rm199 to RM2k++ also got.

the different is inside, which from the outside, the looks is identical because there's only 2 or 3 manufacturer doing the screen and casing.

as for how to see which spec is good, usual customer will only ask how much ram and how much rom, but this can be totally faked.

I has experience my customer with quadcore 2 + 32 selling at rm499 is actually running on 2 core only. The fact is, the CPU are actually a recon unit with 2 core burned and left 2 core running. This is why they sell it at dirt cheap price, dont forget the screen quality and OS quality.

You have to determine by checking, not just printing on the box / spec

1. CPU - i cant tell much, but it's really depending whether they lie or not
2. RAM - 1gb min, now got 4gb i saw
3. ROM - 16gb min, now got 64 max i saw
4. Android Version - 8 / 9 is ok actually
5. Interface (Launcher app) - Interface smooth or not, nice or not are really depend on manufacturer's money in developing. of course more expensive unit will come with more proper developed interface, less problem and more smoother.
6. Sound - Most come with minimum 3 band EQ which is the standard, 12 band for medium and 31 band for software DSP. Currently i haven saw any hardware DSP around. But if you were paring with speaker directly, the sound were fine as china guy now using higher power amp for the headunit. If you want to connect to amplifier, then it's based on luck as the RCA out with Speaker out can be totally different story.
7. Camera input and support - some came with only rear, some came with font + rear, some came with bird view. So it's also depend on price. Lately there's so called AHD camera that can be support by certain model. AHD use digital signal instead of analog signal, so the image will be more cleaner.
8. Extra function from OS (Split Screen, External Mic, Rear view Monitor, TPMS, DVR, and etc.

As said, spec can be fake...300 dun hope can get 2gb at this moment.

maybe share a pic will help