nostr:npub10cq07ulfyc7y2l8rczk9s36g8j65tq3m6xk9us8hr3ua4ktfmaqq9a6nm3 >Are we talking about eyeballs or content ISPs?
I'm referring to internet upstreams that ISPs rent from for internet connections.

https://www.gnu.org/philosophy/words-to-avoid.html#Content

>for peering they require the upload:download ratio to be close to 1.
Yes, the bean counters are constantly on the lookout for chances to start charging the other side.

>it makes sense to charge a content customer for upload only since they barely download.
As the transmission medium is link based and entirely symmetrical that makes no sense.

Sure it's profitable to charge for upload and not worry about download for customers that mostly upload, but merely because something is profitable doesn't make it logical.

Yes, almost all ISPs charge for upload, as that's what the upstreams do - the cost is passed on to the customer.