Do you know when you think "Oh that doesn't look too hard. I bet I can do it in no time"?
That is how I felt when I saw the DIY 3D printer kit Anet A8. It's only 150€ on gearbest so that is pretty cheap.
The reviews said it takes about 3 - 4 hours to build and I though "Ok I am a computer specialist and engineer so 3h sounds reasonable".
When I bought it from gearbest the first problems started: 5 days after the estimated shipping date the packet was still not on its way. After I fucked the support up, it finally arrived 3 weeks after the estimated date.
When I took the first look, everything seemed to be fine except for some small scratches but for that price that is not a problem.
So I started to build the printer at about 14:00 and even if some random sites in the manual were in Chinese I felt confident to get it done in a view hours.
And then it started to get really fucked. The first problem was that 2 screws were unusable and I had to use my own screws instead. The next problem was that the manual was just in the wrong fucking order at some points and I had to reverse multiple steps to get it right.
But the most fucked up thing: There should have been 2 threaded rods with a length of 345mm but the rods had a length of 310mm which was nowhere listed in the parts list. So I had to go buy some aluminium rods to fill the gap temporary so that I can at least go on with the build before getting a replacement. And I could go on and on and with the problems but the point is, it is now 19:30 which is about 5.5 hours after I started and I am still not fucking done with this.

So what have I learned?
Cheap Chinese hardware is good, but only as long as you don't have to assemble that shit yourself.