>I see nothing mentioned about integrating webhooks or some kind of similar feature.

Exactly - nothing so far. But it's impossible to believe they won't.

>If you’re hiring employees, paying under ten bucks a month per user for a full communication suite is not bad.

Yeah, if the Slack is for an organisation of full-time employees, the pricing is a non-issue.

All the cases where it's been a problem are something different: either an organisation of volunteers, or just a collective of people, or maybe an org that has some employees and some contractors who might be inactive for a while etc etc.