Not sure I get this one. You can still run a website with http. Now it might alarm the browser and users. But you can do it.

As for certificates being free but maybe not now. It's actually the other way round. As I recall when https was pretty new the main way was via verisign, and it was not cheap to get one.

The fact you could later get one for free for example via letsencrypt is what made it so everyone could run https (along with the changes that allow multiple certs on a single server with multiple domains).

If it became expensive to get certs again I'd bet a lot of hobbyist stuff would go back to http or self signed and browsers would need to tone down the warning. But, I cannot imagine that happening now. Having most sites encrypted is a good thing.