I can assure you that this website is not hosted on shared hosting. They either have a VPS or dedicated server. Depending on if they are managing it themselves it would be at least $100+ a month for a self managed one. Or, they have a managed one and the price would be triple that. Then the domain, but that is billed yearly or can be prepaid for a few years.

Then they have cloudflare which depending on tier, is another $50-100 a month. Then they have to have a tech team of admins, devs, database admins, etc etc. Average salary for those guys would be 50k+ a year. As you can see, the cost is really starting to add up. Costs can be cut by outsourcing but they have to have a core in house crew. Somethings you just don't want to outsource for a variety of reasons. There are also lawyer fees.

Remember, I'm talking about hosting and managing a site of this size (ie. lots of communities). This website is relatively small, but it's getting up there in size. I do not know all the details behind the scenes, but this is my educated guess. I could be way off the mark here.