Not to mention they make 60+ billion a year after tax. So, they're valued at less than 20x earnings, which is actually low compared to the rest of the FAANGs
In all seriousness though, 20 is not a low P/E. It's just that AMZN's 170 P/E is very, very high. Facebook and Google are in their 20s I believe.
If AAPL were trading at 10x or 12x earnings, that would be low, but still not insanely low.