I’ve found these NetApp SAS Festplatte 6TB 7,2k SAS 12G 3,5" - 111-02374 E-X4064A-R6 ST6000NM0034, that cost only 38€! It’s a brand that I’ve never heard about and I’ve no idea how many hours they’ve worked (I’ve asked and I’m waiting for an answer). What do you think?

Edit: I’ve asked the seller if there is a custom firmware that makes the drive unusable and it answered me saying that they work with any SAS HBA controller. They have worked 1863h and written 130TB (he showed me 4 screenshots of 4 tests of 4 drives)