????以比特幣單價1,100美元的執行價格出售十分之一個比特幣的看跌合約，每一份合約的成本為0.045個比特幣或49.50美元。合約于月底期滿，如果期滿時比特幣的價格超過1,100美元，則各個合約便毫無價值可言。但如果比特幣價格下跌，則合約價值將上漲。

????假設截止12月底，比特幣價格已經下跌到500美元，即在不到一個月時間內暴跌55%。

????此時，比特幣看跌合約的價格將上漲。

????可問題在于：要實現利潤，我最終希望拿到的是美元。

????在正常的貨幣期權交易時，投資者可以將做空其他貨幣所使用的貨幣作為結算貨幣。所以，如果用美元來做空歐元，則在合約結算時可以使用美元，進而抵消歐元價值下跌這一事實。

????但目前在比特幣期權中卻無法如此操作。所有比特幣期權和期貨合約均以比特幣進行結算。這是非常不劃算的交易。原因在于，即使投資者最終從比特幣期權中獲益，最終兌換成美元的價值仍要大打折扣。

????以下是計算過程：

????開立賬戶必須提供0.1個比特幣，按周四上午的價格約合110美元。

????看跌期權的成本為0.045個比特幣，賬戶中剩余0.055個比特幣。

????按照我們上面的假設，比特幣價格暴跌55%之后，看跌合約的價值將上漲到0.12個比特幣。加上賬戶中剩余的金額，目前共有0.175個比特幣。

????而按500美元的單價將比特幣兌換成美元，僅有87.50美元。

????這意味著，即便投資者的決策正確，預測了比特幣泡沫的極限，也準確估算出比特幣價格暴跌跌55%的事實，可最終依然要損失22.50美元。

????投資者也可以通過加大做空投入來減少損失。如果投資者以99美元買入兩筆合約，而比特幣價格還是下跌60%，最終投資者可以獲利15美元。這其中尚未考慮手續費，整筆交易的手續費約為4美元，包括美元與比特幣的兌換費用，此時利潤將降至11美元。

????此外，比特幣期權交易并不像在紐交所（New York Stock Exchange）進行的交易那樣。周三中午，MPEx關閉交易，合約的價格不知所蹤。據稱這種情況經常發生。截止周四早些時候，該交易所仍未公布價格。而且，我與Coinbr的經紀人在會議室計算了相關交易數據，最終我得出的結論是，這種交易毫無意義，于是他主動提出將合約按0.033個比特幣的價格出售給我，這樣一來，0.1個比特幣便可以購買三份合約，而不是兩份。這讓我不由得質疑，MPEx所報的價格到底有幾分可信。

????這或許也解釋了為何近期比特幣的價格會一路暴漲。既然如此，為什么還要費心去做空它呢？（財富中文網）

????譯者：劉進龍/汪浩???

????It cost 0.045 of a bitcoin, or $49.50, to buy a put contract to sell 1/10 of a bitcoin at a strike price of $1,100 per bitcoin. The contract expires at the end of the month and will expire worthless if the price of a bitcoin is above $1100 at that point. But the value of the contract will go up before then as long as the value of a bitcoin drops.

????Let's supposed bitcoins were to fall to $500 by the end of December, a 55% plunge in less than a month.

????If that were to happen, the price of my bitcoin put contract would jump.

????Here's the problem: To book my profit, I ultimately want dollars.

????With normal currency options you can choose to collect in whatever currency you are using to bet against another currency. So if you are betting the price of a euro will fall against a dollar, you can collect in dollars when the contract settles, thereby offsetting the fact that the euro just dropped in value.

????You can't currently do that with bitcoins. All of the bitcoin options and futures contracts are settled in bitcoins. This is a very bad deal. Because even if I end up with a bitcoin windfall, they will be worth a lot less when I convert them back into dollars.

????Here's the math:

????To open an account, it has to be funded with 0.1 bitcoin, which will cost $110 as of Thursday morning.

????The put option costs 0.045 bitcoins, leaving 0.055 bitcoins still in the account.

????After our imagined 55% plunge, the value of the put contract has soared to 0.12 bitcoins.

????Combine that with what is still in the account, and it's now 0.175 bitcoins.

????At a bitcoin price of $500, that's a mere $87.50.

????That means even if you are right, and you call the top of the bitcoin bubble, correctly predicting a whopping 55% plunge in the value of the currency and do all of this, you would lose $22.50.

????You can get around this by upping your bet against bitcoins. If instead you buy two contracts, for $99, and once again the price plunges 60%, you will end up making a whopping $15. And I haven't factored in fees, which would probably run you about $4 for the whole transaction, including the dollar-to-bitcoin round trip, taking your profit down to $11.

????On top of all that, this isn't like trading on the New York Stock Exchange. Midday Wednesday, MPEx appeared to shut down, and the prices of the contracts disappeared. I was told this happens a lot. As of early Thursday, the exchange still wasn't listing prices. What's more, after running through my math of the trade with a Coinbr broker in a chat room, with the conclusion that there basically the trade doesn't make sense, he offered to sell me contracts at 0.033 bitcoins, so I could buy three contracts instead of two with my 0.1 bitcoins. That led me to question just how real the prices MPEx was quoting were.

????All of this may explain one reason why the price of bitcoins until recently has been heading straight up. Why bother betting against it???