This is just a collection of my random experiences I've had with budget filaments while printing. The experiences are my own, so YMMV.
Tested polymer: PETG
NO, absolutely NO. Never buy this, even for free it is too expensive. Mine had random blobs > 2mm thickness in random intervals on the spool, so it was a pure gamble if a print will succeed.
Verdict: Don't ever buy this!
Tested polymers: PLA (regular, glow), ABS
A mixed bag. Amazon has no actual manufacturing capacity, they just buy whatever they can get for cheap and rebrand it. In my case, it has always been great. In particular, it is very slow to pick up moisture, even the ABS could be left out for months without issues.
Verdict: Maybe give it a try, dunno
Tested polymers: PLA, ABS
Good filaments. Pick up moisture very slowly. Maybe this is what is inside the "Amazon Basics" filament here?
They offer a pretty great range of colors and polymers. And most of them can be bought on very affordable 500g spools.
Verdict: Go for it
Tested polymer: PETG
The spools are very neatly wound. The filament prints without issues. The filament has a slightly rough surface, I don't expect that to impact print quality, though.
Verdict: Premium feel for budget price
Tested polymer: ABS
This is an okay filament. It picks up moisture like crazy (visible bubbles after a few days outside the drybox) but otherwise prints fine. I got it on Amazon in a sale for 9€/kg. In relation to that price, it's great. Perfect for when you're doing a lot of "filament hungry" prints.
Verdict: Buy if it's on sale and you have a dehydrator.
Tested polymer: ABS
Solid material. Picks up moisture slower than the Tronxy ABS.
Verdict: *thumbs up*
Tested polymer: PETG (white)
Worked really well. Picks up moisture quickly like most PETGs. I really like the very translucent white, it has a nice, pearly sheen to it.
Verdict: *thumbs up*