David Weaver
If I got expensive individual stones, I used their insurance. I tried to buy a volume of used stones and grade them instead, opting not to insure and then "wait and see".

Out of about 200 stones, probably 160 weren't insured, and 3 broke catastrophically. Maybe another 3 were damaged.

Doing what i was doing, those 3 (catastrophic) made tomonagura after I recut the broken halves into manageable regular-shaped pieces.

If you're going to buy a dozen or two stones and keep 3 that you really like, then I don't think insurance or packaging is necessary. If you buy a bunch in one lot, then sellers in japan do skimpy packaging and I'd pay for protective packaging or they'll all come over having pinballed each other in the box. IF you use buyee's insurance (they're a bugger to deal with if you have a problem and don't buy it, even if they caused the problem), they should make you use protective packaging on something like that, but they don't always.

Far more economical to use it if you buy a half dozen things, pay them to consolidate and have things shipped surface mail (there's a risk there, too, but if you can insure it and have the patience to wait, it should work out).

Not all stones make good tomonagura, either. A very fine slow stone that's a little softer is ideal and two of my three broken stones were that.