Since the introduction of futures, the price of bitcoin has gone up, suggesting that there were more As -- people who wanted to be long bitcoin synthetically -- than Cs -- people who wanted to be short synthetically -- though again it is still early. Crudely speaking, the arbitrage spread suggests that there are also more As than Bs: There are a lot of people who want to be long bitcoin without owning bitcoin, but not so many people who want to own bitcoin without being long bitcoin. (Which makes sense! If you bought a bitcoin and sold a futures contract when Cboe launched its futures last week, you could have locked in a risk-free arbitrage profit of something like $1,200. But if you had just bought a bitcoin, you'd be up about $3,000 by now.) The costs of trading actual bitcoins on bitcoin exchanges -- in terms of blockchain transaction costs, exchange withdrawal limits, etc. -- are significant enough that people who want bitcoin exposure are willing to pay about 2 percent to avoid them.
The Fund generally does not expect to invest directly in futures contracts, option contracts and swap agreements (“Bitcoin Instruments”). The Fund expects to gain exposure to these investments by investing a portion of its assets in the ProShares Cayman Bitcoin Futures/Equity Strategy Portfolio, a wholly-owned subsidiary of the Fund organized under the laws of the Cayman Islands (the “Subsidiary”). The Subsidiary is advised by ProShare Advisors, the Fund’s investment advisor, and invests directly in Bitcoin Instruments. Unlike the Fund, the Subsidiary is not an investment company registered under the 1940 Act. The Fund’s investment in the Subsidiary is intended to provide the Fund with exposure to commodity markets related to bitcoin in accordance with applicable rules and regulations. The Fund will invest up to 25% of its total assets in the Subsidiary. Except as otherwise noted, references to the Fund’s investment strategies and risks include the investment strategies and risks of the Subsidiary.
In order to make sure that you actually have money in your margin account to settle the difference with Mortimer every day, you are required to put up an initial margin at the beginning of the contract. A lower sum, the so-called minimum margin or maintenance margin, is also defined by the broker. If the money in your margin account falls from the initial margin to the maintenance margin, it triggers a margin call: The broker requests you to fill up your margin account to at least the initial margin (of course, you may also put up more).
Note that you could just keep bitcoin on CryptoFacilities waiting to make the trade so you don't have to wait to move the bitcoin you bought over. This is called see-saw arbitrage model, where you keep funds on both exchanges to avoid having to wait. This is fine, but you can't ignore that there is extra capital being used in the play, so it affects your rate of return and capital utilisation. We will not use this method, we will do a full, complete, legitimate arbitrage process.