Good question. One guess is that the total amount of bitcoins mined by a given device is finite due to obsolescence — competition from newer faster devices would push returns to zero in the future. So long as the price of bitcoins falls&#x2F;does not rise, the sale price of the device might be enough to purchase the equivalent number of bitcoins on the open market and still make a profit, and the customers would be none the wiser.<p>There is also another very general problem with selling&#x2F;buying miners (beyond the general suspicion of bitcoin fraudsters): if you buy a money-printing device from someone, why on Earth would you trust them not to run the money-printing device for themselves? You&#x27;d think it only ever makes sense to sell obsolete or broken devices, never the real thing, so why would anyone want to buy any?