#nostr is not blockchain.
Yes it is bandwidth intensive currently.
Media is not capped or scaled on the fly like other social media.
Additionally you broadcast to and pull from each relay you are connectedd to, so if you have 25+ relays the bandwidth adds up.
There are progressive web apps like nostrudel that are better optimised than some f the mobile apps.
The bonus is you can run multiple instances of clients.
So for example if I'm on wifi I use a client with all my preferred relays (count=24)
If I'm on cellular data I use a pwa like nostrudel and have 2-3 relays (2 x popular relay like damus and a mastodon bridge relay)
This cuts the data usage to a more manageable level. (Similar to a mastodon client)
Again app/client settings to exclude auto media loading etc...also help here.
#nostr can be a rewarding experience but it requires more user knowledge and tinkering at the moment, its not as mature yet.

The benefit for me is I'm not beholden to any admin or instance and get to curate multiple feeds through lists (bit like twitter)

So if NAS ever goes down I'm happy to offer some help to migrate anyone to #nostr 
💜 🙏