Any refund will be at the $ price, so a $6k miner would be a refund of about 7.5 btc, or about 0.375btc per share for this GB. Would be a good scam, take btc, wait for value to rise, don't deliver product, refund a fraction of the bitcoins. Not saying this was a scam just saying that it doesn't harm Hash Fast whatever the outcome.
Except that's not
actually a refund. If we paid $6k in USD then yes, that would be a refund. But we paid in bitcoin. A refund is returning to the buyer what they paid, which here is far more than 7.5 btc. I also seem to remember hashfast confirming that refunds would be in the amount and currency of the original payment, although I can't find that at the moment.