Sounds like he already has a hard drive that just needs the enclosure, they can be had for under $20. Why spend $100 when he already had the drive? It's incredibly easy to do and will work just as seamless as yours. But maybe I misunderstood him.
That's exactly it. I have a Synology DS416Play NAS that I upgraded the memory in, but otherwise has worked tremendously well. Thing is, I didn't buy "new drives" when I bought it. I played it cheap, and put 2TB drives from external hard drives or drives I had lying around in it. It's RAID5, and when I have lost a drive, it worked great. But I've wanted to upgrade those drives to faster, more reliable units, and didn't want to spend $200 a drive. So I found a 3rd-party reseller that refurbishes and resells drives, and I got 4TB 128MB cache, 7200rpm drives for $60 each. Each came sealed in anti-static bags, and has worked flawlessly since I got them. I simply took one of my smaller 2TB drives out of the NAS, replaced it with a 4TB drive, let it run the "repair" to rebuild my RAID-stripe set, and then replaced another one. In the end, I went from 5GB of space to 10GB, and I didn't have to rebuild the cluster... the Synology sorted out the new free space all on it's own.
Sorry... long story short, I have a few 2TB and 4TB SATA drives laying around, and as I bought a 2TB m.2 SSD for $240 for my Alienware 17 R3, I thought I'd buy an enclosure rather than spend even MORE money on ANOTHER new HD.