Thanks for all the feed back, everyone.
Buying one at a time was my plan, but when you stumble across something like this you have to think about it. The listing did say they had sustained some rust and such from improper storage, so I was thinking they might be the same TinyRoots stuff or similar that they normally sell, but severely discounted because of minor/cosmetic damage, and the fact that the buyer can't predict what in the kit might or might not be damaged beyond repair/usability. That's often a risk worth taking because two or three decent tools out of the whole kit and it's paid for itself, more and it's a bargain. There isn't a thing in the whole box I couldn't find a use for somewhere, even if it's not used on bonsai.
That said, I think I'll error on the side of caution and just hunt down the right concave cutters like I originally planned. My finances might be caught up, but that just means keeping them caught up long term has become the priority now.