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Answer by Kynan Eng, brain-related research and commercialization at universities and startups:
It would cost about $12.86 billion to buy one of everything on Amazon. I calculated this value as follows:
- According to this link, the main Amazon website offered 488 million items in 2015. Of these, an estimated 479 million are available.
- I estimate the average price of an item on Amazon is $26.86, with an uncertainty (standard error of the mean) of $6.03.
To estimate the average price of all Amazon items, I followed this procedure:
- Click on Random Amazon Product. As the domain name implies, this site gives you a link to a random Amazon product. No, I don't know why this site exists either.
- Discard the product if it is free or not available, but keep count of it.
- If more than one price is available, select the product price highlighted in red (this is the one that Amazon probably wants you to buy). If that is not available, select the first price listed looking from top to bottom, then from left to right.
- Repeat until 100 nonzero items are collected. Yes, I really wasted my time doing this. I thought about trying to crowdsource this data collection, or writing a bot to do it, but that would have been more work.
By the time I had 100 nonzero items, I had collected 104 items in total (100 nonzero price, two free, two ot available). So we have valid price data on 102 items. Below is a frequency price distribution histogram for the 102 items. The median price was $14.16. The number of unavailable items is estimated as 488 million x (2/104), leaving us with 479 million available items.
From the histogram, we can see that most frequently, things cost 1 cent to $5; a small number of items cost more than $100; and once you get above $30, pricing gravitates toward values like $39.99 and $49.99.
Interesting point: One item cost $588.50. If this item is removed, the mean changes to $21.30 with a SEM of $2.36. That outlier has a big influence, but is probably valid in indicating the long tail of Amazon item prices. I also realize that the nonavailable items are not free—they are unknown. So they should not count toward the average; rather, they decrease the total pool of available items. Also, Yuval Hermelin makes the valid point that I didn't include shipping in the cost. To estimate that properly, I'd need to go through the data again—some of the items were MP3s and movies with free downloads. Right now I'm going to be lazy and assume that Amazon is going to throw in free shipping for adding about 35 percent to their Q4 2015 sales figures.
For full disclosure, the list of random products is shown here (data obtained Jan. 26). If someone reading this works in Amazon IT infrastructure, I guess it would be quite easy for him or her to simply pull up the relevant database tables and do this calculation exactly.
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