Quick example, though not an ISP, but the entire Internet archive operates on 60Gbps of bandwidth. So an attack of 250 would be quite a problem.
http://blog.archive.org/2020/05/11/thank-you-for-helping-us-...
Wow, yes, that definitely puts the magnitude of this into perspective. Thank you.
In my defense though! 60Mbps is literally less than one billionth the estimated internet bandwidth these days: https://en.m.wikipedia.org/wiki/Internet_traffic . I doubt there are even one million ISPs, so it still seems relatively "small" to me. It could definitely be bigger than [random company X] can handle, but it seems like it stands a good chance of being smaller than most in aggregate, so even if it's hard for X to support it's not particularly "interesting" in a state-of-the-art way.
And I can completely believe I'm wildly wrong in this. 999/1000+ low-technical-effort ISPs doesn't seem unlikely to me, so 60Mbps could very well be a major achievement as far as I know. I'd be surprised, but... I've been surprised enough that I'm no longer surprised at being surprised. Humans are weird at scale.
Of course, one figure was about capacity and the other about actual traffic, but still.