I haven't used balena but I have worked with other IoT SAAS companies in the past. All these services seem rather expensive for what you get. Other than creating an easy way to push OS updates to field devices what would I get from your service?
Having built a similar bespoke stack in the past, Balena would have been a steal! It gives you the development, provisioning, build & deployment, configuration, management, and even remote debugging workflows out of the box. On top of that, it's built to require web/cloud developer skills, not embedded skills.
To do that, we have created several companies worth of infrastructure, from a cross-architecture container build system, to a bespoke OS supporting many device types, customized docker engine for embedded use cases, container deltas for bandwidth saving, etc. Even simple things like "how do I make sure my device gets DNS in an arbitrary home network" are incredibly tricky, and balenaOS gets it right almost always.
Which brings me to my next point. We are fanatical about support. We take responsibility for our customers succeeding, which means we constantly find and improve sources of friction. Using Balena gets you that backup team, but most importantly gets you hooked up to the flow of improvements we make all the time. Cloud companies charge $15 per server per month for various devops type services. We do very similar things but for devices that are smaller, more diverse, in tougher conditions, with less reliable networking, and ask for just $1 per device per month.
In other words, when I was in the shoes of our customers, producing even a fraction of the value and piece of mind that Balena provides in house took a lot of work, which was money, and that's not accounting for the time and risk of not getting there in the end. If I found myself in that situation again, knowing Balena and not using it would essentially be negligent. Our most fanatical customers are those who have tried to build something like it themselves, because infrastructure is so easy to underestimate.
As a long time customer of balena, I can assure they are a ton for what you pay for.
* faster development times: git push and your code is built and compiled in their cloud (with real ARM servers), and downloaded from your devices. Doing CI/CD for iot is a great experience with balena.
* the support is tremendous: several times I found very specific use cases that failed or wasn't what the balena APIs where expecting, and after contacting the support, they even put me directly with the developers in charge of those areas to discuss if it makes sense to add it as a feature to balena, or if they can provide me a workaround
* again, the support: I have around 10 years of experience with Linux derived systems, but some things still are black magic to me (like debugging problems with aufs partitions). The support of balena goes to the deepest level possible to solve your problem, even if you aren't in the private support tier. You just enable access to your board to support and they get inside and try to find the problem. It's truly amazing. They are even open to discuss how to improve what they are giving you or the tools.
* total control of your fleet: need to set a flag for a client? Just set an environment variable from the api or the dashboard and each device will update its state when they come back online
* amazing tools: the balena dashboard feels as polished as their other projects, like etcher, if not even more. Any kind of need you have (remote access to the device? Proxy to a port in the device? contact the supervisor of the device from a proxy inside their VPN?) they give to you.
And even more, but this is already a long post.