Apple can't move the needle. Even if they did a 20B buyback on top of what they are doing (which they won't but for a second let's dream) that would only be 5% of the float taken in. Not even close enough to move the needle on the stock or EPS.
Apple won't do it because they refuse to let the domestic cash go down to just 20B and they are never brining overseas cash back...never.
When will people learn apple is not a shareholder friendly company. I was a huge apple bull until I finally woke up to this reality. Check how much stock all the top insiders and board hold. This will tell you why you want to sell