Selling my beavers and castors at next weeks sale. Do the buyers want my castors thawed out, before they buy them?

Assuming you dried them already, thaw them out on a paper towel. Some lure makers will by fresh, frozen castor but you probably need to deal with those kind of buyers directly

I would say yes. Definitely yes. Freezing will cause the inside moisture to move into the outer part of the pods meaning that as they re-dry weight will be lost. Your buyer has to estimate how much weight will be lost so they will bid accordingly. If they're looking at and grading castor already well handled and dry they can figure on not having much or any losses to account for, so they can pay a little better.

This why I always say don't take them to your sale in plastic. They will invariably re-humidify in those conditions.

Don't get me wrong, freezing castor is fine but it does take another day or two of drying after you take them out.

I would take them out and hang them on a wire with a fan blowing on them for a couple of days before the sale. Just some air moving is all you need. Take them in a paper bag not plastic, and let us know how you do.