I'll post this as a top level comment, because I think it is crucial: A few people are saying that it is expensive to run a relay but others have done it for as low as $34/month [1]. So unless somebody presents other proof that it is expensive I would say that those posters are either wrong and trying to mislead us on purpose.
Edit: actually the article links to somebody doing it for $18/month.
$18 can be "expensive".
People live in different conditions, have different income and (even more crucial) different expenses.
Not to mention subjective need. I may be interested in a relay, but I don't really need one. So for me 18$ will be too much. 5$? Maybe. (This is about as much as I'm paying for Fastmail right now, for example).
I've also done a full network replica (all the data indexed in a postgres) on a raspberry pi (with an 8tb nvme attached via a hat). Its really not expensive to do . And if I wanted to drop data older than say 3 months, it would be even cheaper still.