Got to love the description...
I have known these disks to work too, they work especially well when you haven't dropped them. Doesn't mean a thing after they have bounced around in the back of a USPS van for several days in a poorly packed box
I think if I were going to shell out money on disks now, especially with larger disks that take a week or more to properly test, I would be wanting something of a guarantee, or at least a low enough price that I would be buying 30% more than I need.
I'm not saying that there is anything wrong with the ones linked to by the op, they may well be fine and come well packed and the seller may also be a stand up person etc, but all of those things are on a sliding scale when buying used. I just see it as a 50/50 risk of time and trouble nowadays when considering buying disks privately. I would take disks from a proper IT recycler that have been cleaned and tested properly, before buying them privately.
I'm totally biased here, but a shameless plug for one of our own is in order:
I can't say enough good things about getting disks from
@TekramCalvin if he has, or can source, them for you
Peace of mind and all that. Drop him a line and see what he can do for you...