As someone who has worked in some parts of southern Africa decades ago, and who recently stopped buying off ali (for everything, but mostly beekeeping equipment) there is a Big Thing you are forgetting to tell: Right And Ability To Repair.
Secondhand nearly always means you can assure quality, because it has survived at least one owner. Probably decades of abuse and repairs. You can see where it was welded. You know it has survived years in heat, rain, mud and under stress.
You don't want that immersion pump of your irrigation, to break the moment you drove 150km home. Even if you can afford to buy 10 pumps and have 9 spares, you still need the time, travel and effort of replacing. Sometimes the Ali stuff is really good quality. Sometimes it isn't and there is no-way to tell.
As a beekeeper: having a hivetool break that moment the bees are becoming angry and you need to finish fast, is worth ten times that €18.00 I saved by ordering Chinese tools. Having a hive tip over because some chinese screws turned over and didn't hold a foot in place is worth a hundred times that €80 I saved by ordering a cheap Chinese knock-off.
I'm not saying Chinese fabrication equals bad quality. But I am saying that a lack of QA leads to varying quality. Which means it can be really good. But also that it can be poor. This downside risk is more than enough reason to often skip cheap Ali orders.