Is a Used 512GB Samsung PM9A1 With 79% Health Worth €20–25?

Check the complete SMART report before buying. The health percentage might be based on NAND writes, operating time, or remaining spare blocks, depending on the firmware. A consumer drive at 79% has probably seen substantial use, but that alone is not a deal-breaker if the price is low and the drive passes diagnostics.

For a game library, that price is pretty reasonable. The PM9A1 is a fast OEM drive closely related to the retail 980 Pro, and 79% health does not mean it is about to fail. Since game files can be downloaded again and saves are often cloud-synced, it is a much safer use case than storing important documents. Keep backups of anything you cannot replace, though.

Keep in mind that the PM9A1 is an OEM model, not a standard retail Samsung drive. Samsung Magician may not support it, and firmware updates could depend on the original system manufacturer, such as Lenovo or HP. That is not necessarily a reason to avoid it, but it makes maintenance less convenient.

I would only buy it after checking for errors, unexpected shutdowns, high temperatures, and a sensible total-written figure. You could securely erase or format it before use, but do not rely on that to fix a worn drive. At €20 for a secondary Steam library, it seems acceptable; at a price close to a new SSD, I would skip it.