Amazon stock trades at a P/E of 910. S&P 500 average is currently around 19-20. Do you really expect Amazon to continue to grow at such a rate that its current P/E is justified?
Amazon's stock trades at a P/E of 910 exactly because it's deferring profit to continue growing its revenue. At some point it's going to stop investing its revenue into growth and start realizing a profit on that revenue. At that point the P/E will come down.
If capital expenditures are reduced just a bit, or if margins are improved slightly, the E part of the fraction will jump and P/E will fall massively.
All of that being said, there are still plenty of things that could go wrong for AMZN.