Cheap optics, like nearly everything else that's cheap, are a false economy. It isn't the glass (well, sometimes it is...), it's all the not-so-visible areas where cheap scopes skimp. Reticules are often thick wires that aren't straight. Adjustment knobs aren't sealed, and the adjustments aren't repeatable. Many don't hold the adjustments, so your zero drifts as you shoot. All too often, the scope will literally start falling apart after a while, with the reticule being loose in the tube, occular bell getting loose, or losing the gas seal and having the scope cloud up.
Many cheap scopes that can stand up 5 years worth of "one 20-round box of hunting ammo per year" will break the first or second time out on an AR, where you may go through several hundred rounds per range session.
I know that when you see the high prices that come with quality optics, you want to believe that you can find a way to spend a lot less for something decent. The facts are, that's rarely the case. Ask anyone who owns a high-end scope (Leupold, ACOG, US Optics, NightForce, etc.) how many cheap scopes they bought originally, and where those scopes are now. I guarentee you, the answer to the second question is almost always going to be some varient of "I threw them away." That was hard-earned MONEY they threw away, but it taught them a lesson that folks are trying to teach you the easy way.
Still, it's your money, so buy what you want. The only one who has to live with your decision is you. Just don't say we didn't warn you. [:)]
-Troy