Remember Facebook getting more and more focus on market Place. Social flavor can become new trend in shopping. If Facebook offer lower fee, lot of Amazon third party seller might switch quickly.
BTW, I hold significant short position here. Created when my various 820-835 short call got exercise. I hold short cover put as well.
Here is what I think peak profit Amazon can generate.
1. Prime:- $3B ( 65M member at 2021 minus Video and other Cost)
2. Retail:- $15B ( Again in 2021, assuming 7% net margin)
3. Hardware:-? (Don't see profitable in near future- although growth might come)
4. Cloude:- $7B (2021)
So at best this can generate $24B after 5 year. After 5 year, Amazon growth rate likely very small 5-10%.
So even then $400B market cap can't justify.
Above scenario when Amazon able to overcome all obstacle. And Unlike Apple or Google or Microsoft, there are many obstacle company facing.
1. All retailers after Amazon to get back their market share. This likely cut margin very very thin.
2. Amazon Prime member getting into habit to order multiple small order. Amazon actually pushed it so show Prime membership value, while long term. Now Amazon want margin and pushing for Add On items more and more, Which I don't think Prime member like. Further push could upset prime users & growth can stall in bad way.
3. Cloud is already getting clouded and there are already prime example where company going away from Amazon, this mean Amazon need to keep price low enough, margin will suffer and yet other will lure big power user away from Amazon with attractive alternative.
4. Hardware focus, Amazon Branded focus can upset others and can become counter productive.
5. Third Party Seller find Walmart/ Ali Baba better alternative if they offer for 3-5% cut instead 15% they pay to Amazon.
Overall Amazon at this level is very risky investment. I am big time short right now and Bring me no fear. Amazon while have impressive growth, Market they focus are always low margin & while they lead incremental changes in industry, Other are not far behind. For Example:- Google Home already seems better than Amazon Echo & Alexa gadget :- reason Google was always leader in Voice AI, Amazon just bring practical application but can't match AI capability that Google has. Do you homework before invest.