Don't be cheap!
Aftermarket lever are usually on of the first upgrade sport bike riders purchase. Not only do they change the look of your bike, but they also change how it feels and handles. This can be a great thing with the right levers, but a nightmare with cheap knock offs.
The best case scenario is a cheap lever will only make your front brake feel mushy. Worse case is they may make your brakes lock up while riding, and cause a crash. They do so any of three ways.
Most common, the guide hole where the master cylinder plunger sits is too shallow. This holds the brakes on ever so slightly constantly. This causes the brake fluid temps to rise, and the pads to over heat, to the point everything swells and locks up.
Another way they do it is some of them either don't have a pivot bushing at all, or the pivot bushing hole is the wrong size. The hole where the pivot bolt goes galls up over time, and the lever begins to stick, causing the same issue as above
And thirdly, they use crappy billet aluminum. No, Not all billet is the same quality. Often their has voids and flaws in it, or it is not even billet at all but rather a cheap casting. These cheap materials often break or crack at the pivot, and can cause the lever to fall off completely during normal use, or jam and lock up the brakes. Sometimes they break at the adjuster, sometimes in the middle.