For $70, it's a good price, as long as they're in decent condition.
Check the hinge, as that's really the spot most likely to have suffered damage. It should have a little wobble, but not too much.
you can get new tips if theirs are damaged, the silicone ones from Apple hold up pretty well, or there are numerous third party tips, either silicon or memory foam. The foam give you a bit better seal and fit, but do need to be replaced every few months as the foam breaks down.
The seal is important, as it helps to block outside sound. A poor seal will also lead to sound quality loss, since they push against the small volume of air inside your ear to make the noise, If the seal isn't good, then when it pushes against the air some of that pressure is lost
You should also find out if it's the wireless charging case. They updated the case mid cycle, the newer ones support Qi charging.
the second gen did improve the sound quality and the noise cancelling quite a bit over the first. You can find those new for $170-180 (retail $250). but only buy from verified retailers, I've seen many reports of people that have gotten knockoffs on here.