Thanks for the thoughtful response! I really appreciate it. I'm doing my best to be as transparent as possible, so here's a very long reply.
This is not a change motivated by short-term needs.
The problem statement is not that we need to fund the costs of delivering push notifications. We need to fund the costs of building Zulip -- the server, apps for every platform, support for a vast range of different self-hosted configurations, etc.
Yes, we are extremely capital-efficient with a small core team who have taken some very big pay cuts to work on 100% open-source software. But even so, we need a business model that makes sense. A business model based on charging a small markup on top of the marginal costs of delivering notifications can't fund investments in the Zulip main experience or the self-hosted Zulip experience.
The main revenue source for Zulip thus far has been Zulip Cloud, and it's proven hard to grow that business, largely due to competition with the $0 price of self-hosting Zulip, which gets you most of the features of Slack Plus ($12.50/user/month).
Zulip needs a healthy model where businesses that self-host Zulip (and rely on the SaaS push notifications service) contribute to its development, just like those that use the SaaS Zulip Cloud service. This doesn't specifically require the same pricing for the two products. But it does preclude a model where Zulip Business only includes push notifications and is extremely cheap.
On the specifics of pricing, we of course have had a lot of conversations with users prior to this announcement. Most of the objections we heard were from system administrators who told us they would struggle to convince their company to pay even $1/user/month -- either because it was a big company whose bureaucracy had "already bought Microsoft Teams", or because they were a startup that had a very very high bar for paying for software at all.
Meanwhile when we talked to leaders who make purchasing decisions for their company, they tend to think about budgets in comparison with other applications that their business relies on, or else compare with fully-loaded costs per employee, which are along the lines of 1000x the price of Zulip Business. Reactions tend to be: "$6.67/employee/month? That's nothing, I pay several times that for X, Y, and Z, which we use way less than our primary team collaboration tool."
If you think it's priced too high, I'd really appreciate it if you chat with whoever at your business would approve spending money on your Zulip installation, get their feedback, and send us an email. There may well be some categories of customers that we missed in those conversations, and specific examples are very helpful for considering whether there's a gap in our pricing model that we can patch.