Interestingly, it's not WD but Seagate:
It's a SAS drive, so we can expect for SATA model to be €50-ish cheaper. And this price is obviously with "early bird" tax and should fall quite soon.
Western Digital Releases 24TB Ultrastar & Gold Hard Drives, 28TB SMR Drives Ramping
So, only Gold series is to be available in stores, which means just 24 TB CMR drive.
All drives are getting out in SATA version first, SAS is to follow later.
What is real technical difference between Gold and "Ultrastar" lines anyway ? 🙄