I got the Ender 3 used, and I've upgraded the bed springs, the hot end, and the extruder. When it works, it works great. I've just been struggling with fine tuning it. It's good for a someone who likes to tinker or needs a back up.
Asking $100
I feel like I'm going nuts. My printer keeps stopping and/or prints keep failing. I got the printer used. Whe. I was using the original hot end, prints would get toward the end of the print and either stop extruding or the print would be flimsy as if it was only printing the walls. I've switched slicers and that doesn't help. (Cura and Orca) I read it could be a clog so I cleared the clog and used a brand new nozzle. Same thing. So people said it might be the hot end. Cool, I changed to a new hot end, the red creality one. Issues keep happening. I read it could be the SD card, cool swapped that, same issues. I feel like the only thing left to swap is the board but like, what else could it be?
I did have issues with the original filament that I was given with the printer. I have swapped to Elegoo PLA Pro and it was great! But I still have issues.