Starter, $59/month, 5 million updates
Growth, $269/month, 9 million updates
Wait, what? To increase the updates by 80%, the price jumps by 356%.
I understand they're throwing in higher processing and custom ranking. That's still approximately the most absurd pricing variance on one plan to the next on a scaling service that I've ever seen.
What you maybe should have said is (speaking from a sales perspective): the reason there's a 356% jump in price, is because of an incredible value proposition step up of 1,000% in what you're getting!
I think that price gap is a classic, and very large, opening for a competitor. There's a ~$89-$129 style plan missing in there, that is a logical step up from $59. That's obviously just my opinion. I also happen to be a big fan of charging more rather than less, in the service space; that under-charging is a common mistake young companies make. And I still can't make sense of $59 to $269 as a step.
I launched a new business in the last quarter. It has a user feed system that is fairly standard. I've built several feed-like features in the last decade. I looked at Stream a while back, having run across it while trying to avoid building my own again. The good news is, I like your product, it got my attention. That price jump between plans, for a very modest increase in service volume, made it a non-starter. It's too easy and cheap to build my own, which then gives me tight control over its evolution over time as well. It's basically impossible at your price points to compete with what I can just do for myself relatively quickly; that $269 product can be run on a low-cost Digital Ocean droplet in terms of its actual resource demands. You're charging for the quality of your software product primarily, and some support, which makes perfect sense. The problem, is that I can build that and scale it to the $899 plan and save myself $10k a year. If you could do 10 million updates at ~$50-$75 / month, with normal plan stepping from there, it'd be interesting. 250k to 350k updates per day is not an immense sum, just 20,000 daily active users can saturate that pretty easily.
However, I can tell you that our features that are hardest to implement in a scalabale way are aggregated feeds (e.g. one message with "tom watched 10 videos") and custom ranking (reddit/HN style ordering with time decay and points). If you're feed system doesn't have either of these features it might indeed be possible to do it cheaper than our more expensive plans.
However keep in mind, a lot of the cost is in the availability and reliability of our service. Basically for every type of server we run (including databases), we need to run at least two to be able to stay online in case one dies. Finally building and maintaining a feed system is not cheap in terms of developer cost (try finding a dev for $10k a year).