Host on a provider which bills per hour. This caps your cost. It also makes your users pissed because you will go down, but if you’re small, you can afford that. If you’re big, you already have scaling options and should have a team to handle ddos.
This seems to mostly hold true to developers also, GitHub manages to survive just fine after all.
For most internet consumers we’re accustomed to poor service so if a page doesn’t load we’ll assume it’s a local problem and try again 20 seconds later, same with buffering, it’s just something that happens occasionally. This is increasing the case for phone calls too. Legacy live tv and radio going silent though is still a major issue, especially on live events.
When users expressed concerns for a similar scenario that the OP experienced on their community forum, Netlify's staff responded with "how likely is this, really?" Only has to happen once to put someone in significant financial harm.
I would even imagine Netlify's target market is small to mid size businesses who really don't need ridiculous burstable scaling capacity at all. Seems like a bit of a trap door for that customer base.
I agree though, I wouldn't host on them as a small business due to that risk, but I am also happy running my own server so I might be an edge case.