One place to look at are web sites dealing with company bankruptcies. They are good for purchasing electronics and tools.
Back when windows and office licenses were bound to a sticker with a key number, I bought a stack of broken laptops for 10€. They were leftovers from an auction - nobody wanted them. I removed and tested RAM and harddisks, and then cut out the bottom of those laptops where the license stickers were. I sold each set of licenses, Windows and Office, for 10€ each, making a good profit. And kept the RAM and HDs that worked for my own use.
Septimaeus@infosec.pub 3 weeks ago
I use LTO4 tapes.
Overall take: slow noisy writes but viable for cheap stable long-term storage.
Note: for each of the components above I set price alerts and waited. If in a hurry, maybe skip tape storage lol