According to USA Today, 5 companies in the Internet Software and Services and Internet and Catalog Retail industries within the Russell 3000 index, pull in 70% of the money spent online. Out of those, two stand out, together pulling in 57%, Amazon & Google. Between those 2, Amazon is a retailer, with its profits only making up 1.3% of the total, while Google OTOH is king in that respect:
Internet profit is even more concentrated than revenue is. Alphabet [Google] generated $16.4 billion in net profit over the past twelve months, which accounts for two-thirds of the aggregate net income collected by all the Internet companies in the Russell 3000.
usatoday.com/story/money/markets/2015/11/05/online-amazon-concentration-internet/75182132/
petri.com/amazon-google-reap-half-every-dollar-spent-online