there are lots of things to look at when determining whethew a bow is a quality bow or not
using an arrow check the streightness of the cam and see if the arrow lines up with the limbs, the limbs should be in line with the cam is the bow balanced or do you have to add a lot of weight to get it to balance
if you use a strait edge on the sides of the limbs they should line up.

does the string track to the center from end to end, what kind of tolerences do the limb pockets have, is there ample amount of fletch clearance between the string and the cables? all of these things need to be taken in consideration. when purchasing a bow.