buying the "cheapest" anything is going to get you garbage. I honestly do not understand the "cheap" mentality.. Frugal, yeah, I get that, but that is NOT the same thing. Being frugal is getting the most for the money spent - being cheap is just that - cheap. you get what you pay for.
No one said you needed to buy "high end", either, but stop trying to get the cheapest you can. Think of it this way - You are making an investment, not buying throw away crap.
As Carl said.. RESEARCH! take the time to learn about the machine you are interested in.. read reviews, read forum posts, find out what other people's experiences have been. Then find a REPUTABLE place to purchase from. They ARE out there. You might pay a few dollars more but it may actually be worth it in customer support down the road.
Ebay - eh, whatever - research the seller at the very least.
Gearbest?? seriously? OMG no - they are fine for some things, but printers? hell no..
AliExpress, alibaba, and any others like them? Again, Hell No!
I currently have 5 printers... 2 used SD4s, 2 kit printers from Folgertech (had a 3rd one but sold it) and I have a beta tester machine that is a higher end unit.
For the price, the Folgertech kits are not bad. They are not perfect but they are not bad. Better than some of the crap being sold as "assembled" units.
SD4 #1 & #2 - Lawsy carriages, E3D v6, Rumba controller board, mirror bed plate, X motor fan, upgraded PSU & Mica bed heater
SD4 #3 - in the works ~ Folgertech FT-5, rev 1
Printit Industries Beta Tester - Horizon H1