Captain Obvious,

since I have tested serveral different extruder here in my printer(s) I can tell you that building a hotend is much more difficult as it seems to be. That said I personally have experienced that most of the Chinese extruders or even hotends of quite poor quality. Basically they SHOULD work, but most of them are not build precise enough e.g. the tube to guide the filament is to short and does not fit properly into the nozzle... the hotend become clogged and in most cases you´ll be unable to clean it without demaging the tube again. Most of the "engineers" building cheap extruders doen´t even know about the different sections in a hotend having different temperatures aso.

In the hotend I currently using I´m able to print ABS at 242°C WITHOUT a fan or a metal heatsink - it is just well designed...