In what universe is their sync service cheap?

It's literally at least 100 times more expensive that Dropbox/OneDrive/Google Drive/iCloud sync

My assumption is that most people on HN are making programmer money. $4 - 5 USD per month is affordable even on a junior engineer’s salary in many parts of the world.

The price per GB isn’t as good as the services you mentioned, but their storage limits are fine for the primary use case — storing a lot of plain text notes.

I’ve also had no problems with it, in contrast with iCloud which has routinely gotten stuck for me.

And if price per GB is what you care most about, use something else. That’s one of the great things about Obsidian.