I am spoiled to have utterly unlimited data at extremely high speeds, but usage is a serious issue for several friends I have on here.

How would this work with the duplication from several relays? Would the relay report it and the client estimate the total?

For me personally 300MB is nothing. I have 180GB included in my mobile plan and 3TB included on my home Internet plan.

For users that do have limits though I think the solution is more trying to optimise clients to reduce the data usage, maybe through caching or avoiding pulling duplicate notes etc. I’m not entirely sure how feasible that is.

If there was some sort of metric for how much data a person produces maybe it could be possible to put users over a certain number of MB in a list and only pull their notes when connected via wifi rather than just not following them.