With Damus it is quite the reverse: ~30MB per 1min session! 😱
Discussion
For a rich-ui client, that might not be too bad, I'm not sure. I know it could do better since it isn't using NIP-65 style relay tracking, but referenced web content is probably much heavier than the sizes of the events themselves, and if it caches (I don't know if it does) then it might not be able to reduce that number by much.
I'm lucky on this front since gossip doesn't pull/render any content from the web (other than Avatars at the moment). I don't think clients like Damus should take that approach, so Damus will always be expected to pull a lot more data.
But these numbers can get very high. One user reports that Amythest used 48GB over 10 days of usage.