@drfate786 I think you have a major misconception about what Alpha and Beta testing is about. Developers are the ones that go through and test the way you seem to think Alpha testers should be doing.
Alpha testers, followed by Betas are there to give a smaller than full release sample audience testing environment. A small, usually invited group of testers who play the game as if it were in full release, knowing it's an Alpha/Beta so they don't necessarily complain about what would be finished product issues, but rather, go through the mechanics over and over en masse in order to reproduce common bugs that the end users will thus not have to deal with, as well as ironing out mechanical interaction issues that a controlled tester might NEVER find because of their more controlled, systematic method of playing the game. Often bugs and exploits of said bugs are discovered because the 'player' did something not expected by the development team and thus triggered an unforeseen outcome that they might be able to use to their advantage, or conversely, might ruin their account and make them start over completely.
Also, as Logain said, QA testers aren't developers, they are paid in-house testers who are just sometimes given specific assigned tasks to go over for bugs, and the only real required skill isn't being an expert coder or even gamer, but rather the ability to write a detailed bug report. They are underpaid, and frankly, if these guys were to find an actual Exploit in-game, if they thought they could get away with it, just like any other player, they might keep it to themselves to exploit when the game goes live for their own benefit anyway.
The fact of the matter is, by running an open Alpha/Beta test cycle, the developers save money on paid testers, AND open themselves up to a much more rigorous testing process, as these 'un-paid' testers are going to run the game through a much harder workout than a 9-5er playing the game for a paycheck.