A 3d printer is a tool. No different than a lathe, table saw or drill press.. Buy cheap china crap and you get what you pay for.
Need I say more.. Well yes I will.. It is not like printing a word doc.. Not only do you need to design your model for the type of fabrication you plan on using, you need to learn how to fabricate it.. I.E. configure your slicing software...
In the end the answer is you get what you pay for and you get back what you put in..