I don't think that matters really. Maybe companies that are already using slack won't switch, but if you're using chat, which is free, are the executives really

I don't think that matters really. Maybe companies that are already using slack won't switch, but if you're using chat, which is free, are the executives really going to decide that it's worth paying to switch to slack? I think it's unlikely. Hard to see where the market is other than startups that are already using slack. Slacks revenue is currently nowhere near enough for this valuation and I can't see it getting where it needs to.