[T]he two researchers identified a few factors that could help answer the question: market value, replacement cost and consumer value. They looked at what other sites that get similar traffic are worth, how much people would be willing to pay for Wikipedia if it weren’t free, and how much it would cost to replace the site. In the end Band and Gerafi conclude that the website is worth “tens of billions of dollars” and has a replacement cost of $6.6 billion dollars.
For context, it costs the site $25 million each year to run. And for comparison, Twitter’s recent IPO announcement has their company valued at about $12.8 billion. Band and Gerafi write, “The millions of hours contributed by volunteer writers and editors leverage this modest budget, funded by donations, into an asset worth tens of billions of dollars that produces hundreds of billions of dollars of consumer benefit.”