I did do a series of videos to setup a basic ubuntu NAS:
DIY NAS - SwiftNAS - YouTube
That's very nice of you, I believe people interested in building their own NAS will certainly find your videos very useful.
No worries, I didn't ask the question because I want to know how. If anyone can pay me, I can even built a Highly Available NAS solution that works between 2 systems to ensure extremely high uptime.
I just find sometimes people underestimated these consumer solution outside thinking that it's a simple solution.
One is power consumption, good NAS solution can offer extremely low power consumption through specially chosen PSU of small form factor that is not easily available. Also they come in niche form factor with multi bay slots well placed with the best intention to save space and also provide good airflow. Having good airflow also means less powerful fans require to properly ventilate the heat. My synology doesn't even purr(virtually no sound) in the middle of a silent night. I can't say the same for a self build NAS that runs 24by7. Also the integration with a UPS is not necessarily easy. Not all mainboard's sata controller are hot-pluggable. Compliance to AHCI doesn't' necessary mean hot swappable.
It's also not a brainless feat to expand a DIY NAS by adding new drives to expand the volume size, migrate from one RAID to another, or even harddisk failure replacement.
All these while can be achieved in a DIY NAS are not in comparison easier than a commercial NAS. Also I don't suppose everyone that wanted a NAS is also a linux user. Who can Windows free ? Can you compare the resource of a Windows OS to a console server linux ? Which means no UI for the person performing the DIY, all pure console instructions ?
So you see, sometimes all these convenience are not cheap, that's why a good NAS is not cheap.
I know one can argue I don't need all these stuffs. My answer to this argument is simple
"
There is a difference between you don't want and you don't have".
That been said, I'm not discouraging anyone adventurous enough to try DIY your own NAS, but rather be sure you know what you are doing. People buy a NAS other than convenience, also include things like they can't be sure if the DIY NAS they built can withstand real disaster when the NAS fails or the harddisk fails. Without these knowledge, there is no good value to built your own NAS when you cant secure the reliability of your data.
Hence if you don't know how all these things work under the hood, then get a commercial NAS. Let the experts deliver a proven product to you. If you understand all these technicalities, feel free to get your hands dirty. It's always a trade between EFFORT and COST.