Even at $502 as of this post, Apple's stock is still a bargain according to Slate.com:
Not only is Apple not peaking, it is likely not even close to reaching its potential earnings in its two biggest markets, smartphones and tablets. Indeed, I suspect that one of the reasons Apple’s share price is so low is that it has been difficult, on a purely perceptual level, for investors to understand the financial opportunities the company is poised to realize. The numbers are just too big; it simply doesn’t seem possible that a single company could capture such a large part of the market. But not only is it possible—it is happening. The iPhone accounts for only 9 percent of the market share in smartphones, but Apple is earning 75 percent of the profits in smartphones. Its dominance in the tablet market is even more staggering.
Plenty of "I wish I woulda bought when $AAPL was at..." Time to get a group of friends together and buy a single share.