I think the value is what needs to be refunded. That is about 40BTC right now. That way, no one is really at a loss. Of course, my reasoning falls apart when you consider that if the price of gold doubled then it would be ok to send only half an ounce; if you consider things as only the value they represent. But, Gold is a commodity and Bitcoin is a currency. Bitcoins represent buying power, and so if 40 BTC were refunded then the gold coin could just be bought elsewhere. This way no one could hedge anyone (as far as the currencies are concerned).
WTF? Scenario:
- Buyer pays you 100 BTC for something.
- BTC's worth doubles in USD.
- You don't send what Buyer ordered.
- Buyer (obviously) wants a refund.
- You'd then try to only owe Buyer 50 BTC?
The only one getting screwed would be the Buyer. Comparative value is meaningless. The Buyer cares about what he paid in his/her bitcoin. Alternatively, if bitcoin became half as much in USD, Buyer would still be owed 100 BTC. How is it possible to not see how unfair it is to be refunded in anything other than the original amount?