It's a good price but still feels wasteful if you also run/pay for nextcloud or similar.
And the notes are all just markdown files. If the obsidian software were to disappear you have all your notes. It's fine someone wanted to spend a load of time writing their own software but none of the reasons presented in this piece make sense.
As long as I'm paying for it, I'm the client and not the product.
I tried some of the third party stuff, iCloud, Dropbox, etc and with all of them I either lost data because of notes not being in sync or had to manually fix stuff. $4/month and zero issues was well worth it for a tool I literally use every day.