R&D is but then isnt even an excuse I dont think cause its only about 8% of their revenue. Their gross margin is about 27% compared to to Ebay's 65% though. That's the real difference right there. Something is fundamentally wrong with Amazon's business model.
the problem is that Amazon operates like a regular retailer ala Walmart, Costco, Kroger etc. but is treated like a tech company.
Where a regular retailer doesnt require R&D but instead maybe some Marketing, CAPEX and Supply Chain refinement, Amazon requires all of the above.
You take out that $6.5B in R&D and the profit is albmost $7B for a P/E of 21. You cut that R&D in half and still the P/E is still in the 40s which is very reasonable given its revenue growth. This is what I've come up with glancing over its financials on Google finance
That being said I would never buy the stock; but if it was given to me I would hold it gladly.