Nothing beats those old Sharkoon cases with the 9x 5.25" bays in front imo. 90€ or so back in those days. Add some hotswaps to it. Maybe look online for some old builds that use it?
Data Hoarder
We are digital librarians. Among us are represented the various reasons to keep data -- legal requirements, competitive requirements, uncertainty of permanence of cloud services, distaste for transmitting your data externally (e.g. government or corporate espionage), cultural and familial archivists, internet collapse preppers, and people who do it themselves so they're sure it's done right. Everyone has their reasons for curating the data they have decided to keep (either forever or For A Damn Long Time (tm) ). Along the way we have sought out like-minded individuals to exchange strategies, war stories, and cautionary tales of failures.
https://aerocool.io/product/cipher/
12 slots and costs 90€ (in Germany)
It came out as the cheapest option for 12+ slots cases. You can compare here: https://geizhals.de/?cat=gehatx&xf=14070_12&sort=p#productlist (only if you're German or at least in Europe), don't know about price comparison sites in other parts of the world with as many filter options.
I dont have enough karma for posting, sorry for (sort of) offtopic. These arn't cases, but cheap hdds.
https://www.ebay.com/itm/284905935981 12,94€/TB
https://www.ebay.com/itm/295923852343 12,50€/TB
Fractal Design 7 can easily hold more than eight, but you'll need more fans and trays.
Rosewill 15 bay server case
Good option but it costs more than $150
Jonsbo N3 is a nice case if you need something ITX
I have a fractal xl2 and managed with some diy to get 20hdd inside
Hi, I bought this one on Amazon with special deal:
Inter-Tech 4F28 Mining-Rack ATX. It’s for 28 HDD and 2 SSD. With good PWM fans makes low noise.
I really like the Fractal Design Node 804 which will hold 10 drives and will likely be the next case that I build in.
You could also go with the Phanteks Enthoo Pro 2 which should hold 12 drives.
The problem you will run into after reaching a specific amount of HDD slots are for one the slots to connect those on the motherboard, which can be upgraded by a raid controller. Next issue are your lanes you using on the board... NAS not an option?
Add more bays to your current case:
https://www.mountainmods.com/product_info.php?products_id=326&osCsid=7ho2gmel0j8tm6kb7p9kn36e25