Stock PS4 drive has 408GB usable space. (Read the image in OP)

Defrag if old.

Stock drive is 500GB.

323GB free + 84GB games + 100MB other = 408GB.

Applications is only the three games. Nothing else installed/deletable.

As others have pointed out, 500GB is a marketing number. The OS sees GB (and MB, KB) in chunks of 1024 compared to a straight 1000 multiplier. e.g. 1GB = 1024MB, not 1000MB as marketing reports.

Thus, 500GB /(1.024^3) = 465 "real" GB.

1.024 is the ratio factor which is cubed because it's used three times: Bytes in KB (1024 vs 1000), KB in MB (1024 vs 1000), and MB in GB (1024 vs 1000).

That means 465 - 408GB leaves 57GB reserved on the drive. Not all of that may necessarily be occupied. There is likely a swap partition, the OS, reserved space for game clip sharing, etc.
I was hoping to upgrade the PS4 HDD to a 1TB-or-so one and use the PS4's HDD to replace my PS3's 80GB one, personally.

I do intend to buy games physically, but PS+ games add up quickly, and I never liked the fridge-organizing with Nintendo; wouldn't care for it here, either.
With the lack any media support ( I still think this is stupid ) I doubt space is gonna be a problem with or without an upgrade this year.
Go, go 1.5TB hard drive on day one. Yeah it's only a 5400rpm model but it was cheap and my laptop is right beside me so I guess I can look at some tits or something while the next map loads in BF4. With thieving ass Comcast "testing" out a 300GB bandwidth cap in my area, I doubt I'll be downloading a bunch of games each month unless I add them to my download queue and space them out each month.
Expected. It is why I laughed when that kid who got the X1 said there was 500GB of available space. Nah.

It will be similar, if not worse, on the X1 with all the built in apps and the 3 OS's and everything else going on.
yeah am going with physical discs next-gen too
On both systems you still need to have hard drive space for the games. Both systems install while you play. You can of course delete the game data and it will just reinstall when you put in the disc next.

Also, this isn't too surprising.

Don't forget that marketers also define 1GB as 1000MB. In reality, 1GB = 1024MB (technically that's known as GiB and MiB). Thus, a 500 "GB" hard drive actually has a maximum capacity 465.6 GB, which is what the OS will show.

Thus, the OS is not 100 GB like someone mentioned below. The OS + system apps is 57.6 GB.
I'll have to replace it anyway. Same portable size hdd as PS3? 2 TB would be enough.

And can I still copy my videofiles to the PS4 in my bedroom? No mediaserver sucks.
I know it's kind of a silly thing to complain about but how can memory manufacturers and Sony in this case get away with this? Especially in EU? They are clearly misleading the consumer.
I guess they need to keep a cache space the size of a full blu-ray disk? Didn't I read somewhere about game caching?
Games are cached to the portion not walled off for the OS. They are installed, they are just using the term caching to make people understand that you don;t have to wait an hour before you can play.