Note the date on that is Aug 16 2013. Since then, BTC/USD has fluctuated by ~800%. HashFast does not owe you an 800% windfall, and no judge or arbitrator is going to award you one.
Build a bridge and get over it.
Note Hashfast claims right to violate any past promise with no sense of shame. Promise made seconds ago? Tick tock, invalid already.
Now if I'd dropped a quarter ounce wedding ring off at a jeweller for sizing, they said it would be ready in "two weeks" and by the end of the month gold had gone to $10,000 an ounce, I don't think a court in the land would see their "point" that you "only" left a 3 or 4 hundred dollar ring with them, and they shouldn't now "owe" you a $2500 one.
Especially if they signed the agreement to return gold to you if they don't manage to size the ring.