So the monthly cost for everything is around €9.50, more or less this should be the cost, I have not converted the cost of the domain into euros
I'm not any expert, but I think $10 is a good number! Even my electricity bill comes down to $25-40 (monthly), and my wifi costs around $8-10, so this is most likely a good deal.
Now if you have a good enough desktop, you can reduce the cost of VPS by running your own VPS. Although, the setup would require non-stop internet, electricity and backup power in case of power outage and a bit of technicality, but it's definitely possible. I believe you have already experimented something similar with your mobile device. Am I correct?
But again, you already have a good numbers on the cost, and running your own VPS might be a hassle! Anywway, you could always experiment, to quench your curiosity! That door is always open!
I just love testing out new things you know. Unlocking the bootloader, flashing custom recovery, then CustomOS, rooting my device via Magisk or KernelSU, even installing Kali Linux one time (on a mobile device). I have tried all sorts of weird things.

Yes, your idea is not bad, and it could be much more convenient for me, but it would increase my commitments enormously, and we only have one PC in the family, so I should buy one specifically for this purpose. I had a Raspberry Pi but it passed away this summer. There are many things to consider before turning a PC into a server.
I think less than €10 is an acceptable amount to manage a website.