About ten years ago, Jimmy Wales said
about Wikipedia (time code 4:35):
“So, we’re doing around 1.4 billion page views monthly. So, it’s really gotten to be a huge thing. And everything is managed by the volunteers and the total monthly cost for our bandwidth is about 5,000 dollars, and that’s essentially our main cost. We could actually do without the employee
... We actually hired Brion [Vibber] because he was working part-time for two years and full-time at Wikipedia so we actually hired him so he could get a life and go to the movies sometimes.”
In 2008, when Wikipedia was already the world's number 8 website, the Wikimedia Foundation survived on $5 million
(vs. $82 million last year). So, yes, you can have a top-ten website – written entirely by unpaid volunteers – for a fraction of the current cost.