It depends entirely on what you want. You can literally code a JavaScript 1-liner that will make a <textarea> then put the content back in the URL and it will work serverless on pretty much any platform with a Web browser.
You can also write a note taking app that will be federated yet private, that will have its own scripting language, etc. I mean you can yak-shave your way to write your own OS or even designing your own CPU for that.
So... I'm not sure that metric, time, means much without a proper context, including who does it. It's quite different if to do that, regardless of the tooling used, if you are a professional developer, designer, fullstack dev, prototypist, PM, marketer, writer, etc.
sure. does your note taking app supports formatting? you don't need it today. you will need it at some point. images? same.
does it handle file corruption etc? no? then its pretty much useless.
does it work across devices? in modern world, again, it is pretty much useless without it
it works across devices? then it needs hosting. if it is hosted it needs auth, it needs backups
you can go on for ever.
the bar for very minimal note taking app that you actually will use is very high, with other software it is even higher.
and this is not even state of art, this is must haves
And even so if your starting a note taking app most of those problems like file corruption and image support are largely solved problems. There is also the benefit of being able to reference tons of open source implementations.
I think one month to notion like app that is prod ready if you just need Auth + markdown + images + standard text editing
Bad example, note apps loaded with features are anti-productive and are for people who treat note taking as a hobby itself.
You have Obsidian anyway if you want something open source to work with.
When everyone is able to make their own one off prototype in 30 minutes, no one will pay for the thing that took someone 6 months.
there is very very rare use case when diy makes sense. in 99% of cases its just a toy that feels nice as you kinda did it. but if you factor in the time etc it is always costs 100x more than $5/month you could usually buy
In late 2024 it might have taken 6 months. Today, two weeks, maybe 3.