I definitely felt the same way when I was shopping for my first NAS. A two-bay Synology ran about $300 for new on Amazon and I just couldn't figure out why it was so expensive.

A few months later I picked one up used on Ebay for $120, and after using it for a few weeks, I can now report why these cost so much.

The amount of software that comes on this thing is absolutely mind blowing. I was able to set up a bidirectional sync to my cloud drive, differential backups, compressed folders for archival, and a backup to Glacier for off-site backup without writing a single line of code.

With a bit of additional digging into their package center, I found out I could install Docker & run GitLab on the NAS, along with a bunch of other self-hostable software.

I realize I could have probably built my own NAS and used FreeNAS for a fraction of the price of buying new, however the amount of time that would have spent configuring/debugging/setting up FreeNAS makes the vendor-purchased NAS a much better investment.