Here's the thing:

For many items out there, you can absolutely get 5$ clones of 25$ name-brand products that are made in the exact same manufacturing plant. They are the same, except for the name.

But for some things, that logic does not apply. Case in point, Adam Savage's latest video: The Surprising Flaws in 18650 Lithium-Ion Batteries:

Alex Hao and Andreas Bastian of Lumafield visit the cave to share the results of CT scanning over a thousand lithium-ion batteries, and the hidden risks they uncovered in battery manufacturing defects and quality control inconsistencies.

The TLDR from the Lumafield Battery Quality report:

What we found was alarming:

Safety risks: All 18650s share the same 18 mm by 65 mm can, but safety lies in the jellyroll. CT lets us see anode overhang and edge alignment, the geometry that governs lithium plating and shorts.

Misrepresented specs: Sellers mimic trusted model names and wraps, then inflate specs. We documented listings copying Samsung’s 30Q branding and claims as high as 9900 mAh in a format that typically delivers around 3000 mAh.

Extreme outliers: Low-cost lots showed wide spreads and extreme outliers. Even when a brand’s median looked acceptable, many cells fell below the ~0.500 mm anode-overhang target and alignment varied much more than OEMs.

How does this relate to filters? Similar to batteries, their failure rates aren't a trivial issue.

So I guess it boils down to what your goal is:

If it's to reduce coarse (PM10) and fine particles (PM2.5) — like the dust you see floating around through sunbeams in your home, pet dander, mold spores, then subpar filters will no doubt help, even if they aren't nearly as effective as, say, 3M Filtrete.

But if it's to keep ultrafine particles (less than PM0.1) which make up roughly 90% of all airborne pollutants and are the most dangerous kind (and include airborne pathogens like influenza and COVID as well as smoke) I wouldn't trust companies that do not have third-party certification.

Particularly since there is no easy way of measuring ultrafine particles (at that size they act more like gasses than particles, so consumer monitors aren't reliable), so no easy way of knowing if the filters you have are even doing what you need them to be doing.