I've got about 100k pageviews a month (according to NodeBB stats) with a pretty small number of users (apparently they are really active though). My $10 DigitalOcean server is probably more than enough for that. I'd imagine I could go down to the $5 one if needed.
You could go to $5 on Vultr for sure. Anything you can do on DO, you can do for half that price on Vultr or Linode.