95% is absolutely not accurate. Amzn's latest annual report (put out April 6th 2016) states ”close to 50% of units sold on Amazon are sold by third-party sellers."
As mentioned, Amazon tends to list the top 10 products in most categories, so naturally they'll get a lot of units sold, but the overwhelming majority of all products listed on Amazon.com are 3rd party sellers.
You can look for yourself, it's fairly obvious.
> Nearly everything sold on Amazon these days is 3rd parties. I'd wager somewhere in the 95%+ range
And again... don't take my word for it... go take a gander yourself. It's very obvious once you look at a few products...