With many of the used radios I've purchased they have come with used battery packs, condition listed as unknown and no guarantees about capacity. Normally I don't consider the inclusion of a used battery pack of much value due to this issue. So before doing anything with a used battery pack I test them, then label the pack with the measured capacity. If they test at 80 percent, or better, I consider them "good" for general use. If the included battery pack tests good then I got a slightly better deal that I had originally thought. Typical no name brand battery packs for my radios run around $20 to $30 new depending on capacity.
Most of the used battery packs are the newer Lithium Ion type. I did end up with some used Nickle Metal Hydride and Nickle Cadmium packs. The Ni-CAD packs are about worthless. They suffer from memory effects and get buggered up too easy. If a seller includes a used one it adds zero to the value of the deal IMHO.