If I have let’s say 50 Kirby websites, how mutch work per year will it be to maintenance those websites and what will Kirby updates cost?
Cost I’d say it’s only an issue when Kirby 4 comes out and I doubt that will happen anytime soon, not in the next couple of years at least. And we can speculate how much an upgrade license could cost, I think last time it was 29$ but I could be wrong.
Let’s just say for the sake of this argument that an upgrade to Kirby 3 to Kirby 4 is 50€.
You’d have 2500€ in licenses down the line.
Then there’s the maintenance.
So Kirby is not really backward compatible with PHP versions since they’re thankfully very aggressive when it comes to supported PHP versions. Right now minimum required version of PHP is 7.4 that was released on November 2019 and will reach end of life in 2022.
If you set up a server now with PHP 8.0 I’d say that you don’t have to worry about that aspect for at least a few years, so that’s a non factor. You obviously should want to stay up to date but what I’m saying is that you can theoretically set up something where you only have to worry about updating the server every few years.
Then there’s the issue of updating Kirby itself. I’d argue that you don’t have to update to each new version. Once a site is live, if you don’t need the new features you can safely skip a few versions (not the security ones though) so you can realistically update your 50 sites every 3 or 4 months I’d say.
Now let’s imagine it takes 15 minutes to update a site (to check it locally, make sure everything works, update the live version, make sure that one works and so on)
so that’s 15 minutes * 50 sites, 750 minutes or 12 and a half hours.
So you’re looking at ~ two days work of work every 3 or 4 months.
This is just a very back of the envelope calculation but at least you have a rough idea.
Forgot to add that between an update and the other there could be some breaking changes so you also have to take that into consideration.