HDD drives such as this one tend to be cheaper than an SSD drive, but they're not as fast. Potentially a perfect choice if you happen to be looking for an HDD drive.
From ServersPlus
WD WD Purple WD43PURZ 4TB 3.5" 5400RPM 256MB Cache SATA III Surveillance Internal Hard Drive
Getic
Western Digital Purple HDD SATA 4TB 5400 256MB
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