I thought it was in the TOS that refunds were to be in USD at the price of the Baby Jets or in BTC at the amount paid and at the discretion of the customer so long as there were enough other people on the wait list so there would not be unsold Baby Jets. But I am not aware of any screenshots or prints of the TOS so that returns the BTC exchange rate issue to irrelevance.
Consequently, I think it will be very difficult to find an attorney to take this case and even more difficult to find one to take it on contingency because you will likely lose.
Hey Sunnakar -
The USD exchange rate wasn't listed in the TOS at the time of sale... however my receipt had the following text on it.
Your order is expected to ship between October 20 and October 30, 2013. Physical delivery of your order will take place within days, depending on the shipment method selected. HashFast guarantees that all "Baby Jet" units from our first production batch will be delivered by December 31, 2013. If Buyer ordered one or more Baby Jet units, and HashFast does not deliver such units by that date, then Buyer may at his or her discretion, cancel the undelivered portion and HashFast will issue a full refund the payment for the units that Buyer purchased but did not receive and cancelled. This cancellation and refund is Buyer's sole and exclusive remedy for HashFast failing to deliver by the December 31, 2013 guaranteed delivery date. Buyer must cancel the order and request a refund by January 15, 2014 to avail him or herself of this remedy. Buyer to pay all taxes, duties and shipping costs on units delivered.
"full refund the payment" ... the payment was a BTC payment.