I have been running my own web site for 20+ years without ads. The server and bandwidth costs are minute. I use a basic VPS. I started it when I was still a poor grad student. This is cheaper now than shared hosting was back in the early 2000s and it's easier too. But it's not cheaper than "free" and it's significantly more administrative work than just using a social network. The "people" costs (including my own time fiddling with software configurations) is the biggest barrier.