Slack has a network effect for any user that is part of more than one group. If it's just one group for work, sure, the company could switch and gone is the user. But if that user is part of other groups they will push back against the switch as no one wants more chat windows.
Who pays the Slack bill? It doesn’t matter if the network effect doesn’t accumulate value toward the entity making the buying decision.
What Slack has is a golden brand and a price point that apparently doesn’t make companies look much further than that.
It smells a lot like New Relic in that sense. Eventually the pricing catches up and new signups start dwindling and despite a good deal of lock-in companies think about switching.
Slack is very nice to use. Users love it. Those who negotiate and pay the bills (like me) are surely keenly watching for any credible competitor to get out from under the fairly "fully priced" (to put it as politely as I can) offering from slack.
