I work with a lot of different companies. They almost universally have Slack instances that get used for discussion. One time I was working with a client who was too tight to actually pay for their Slack instance so it had amnesia.
For a while I was really grouchy about it. Then one day I was thinking along the lines of "Ah this is such a PITA. I've just had this good discussion about these requirements in Slack but because it's not a paid instance it'll vanish in a few days. Grr I'll have to take this information and put it somewhere else. I guess I'll stick it in a design document in the project's wiki. This is such an inconven... wait. Huh. That's vastly better than leaving it floating somewhere in Slack. Oh."
And in that moment, I was enlightened. Paying for Slack actually makes it a worse tool.