The reasoning is that...
1) the thing(s) has been around for far too long without selling, either because the owner or the items are cursed, or both
2) the owner needs to punch out NOW, of his current location and the endless burden of curating effectively a museum of the thing(s)
3) as BTC deflates, the owner can exchange to fiat as soon as the amount of BTC reaches the original fiat value he wanted to sell the thing(s) for
With those things in mind I wouldn't go lower than 75% . . . 70%
But with that said, BTC is currently sky high and you might have to wait a long time to get your investment back.
This wouldn't worked perfectly if you had done it last week though xD