Is the statement in the linked article that "The Internet Movie Database functions as a loss leader for the e-commerce giant" backed up somewhere?
IMDB offers both Pro Subscriptions. IMDB offers data licenses that the company claims are licensed "to a wide selection of businesses including movie studios, cable companies, websites, video retailers, software developers, electronics manufacturers, mobile applications, and more."[1]
IMDB offers advertising and has 250M visitors per month.[2]
None of these point to the likelihood that IMDB is a loss leader.
1 = https://help.imdb.com/article/imdb/general-information/conte... 2 = https://advertising.amazon.com/channels/imdb
It was initially purchased as a vehicle to drive customers to Amazon's DVD sales business. I think it's monetized itself pretty well since then, though.