you have to stop "thinking" in USD. hashfast received BTC and shouldv'e kept those, for refunds. simple as that. they don't care about other currency's value, so we don't as well.
So then, what should HF have done if they kept the customer payments in BTC and then the value plummetted to $25? How is HF supposed to pay their bills once the hardware materializes and is ready for shipping? How do you then curb users demanding the equivalent $5,000 in BTC?
The only solution is to stop the pre-order game or don't take BTC unless you can ship the unit, or make it ABUNDENTLY clear what the rules/regulations are and STICK TO THEM.