I am interested in deeply understanding the way ETF market makers operate to profit. I already know that market makers profit from buying at the bid price and selling at the ask price, and I am also aware of the creation/redemption mechanism that allows them to make a profit if the ETF value deviates too much from the NAV. What puzzles me is how they use hedging to 'instantly lock the bid ask spread profit', as I have read in many different places. For example, the following paragraph can be read in a Virtu Financial's repot - emphasis mine:
Our strategies are also designed to lock in returns through precise and nearly instantaneous hedging, as we seek to eliminate the price risk in any positions held. Our revenue generation is driven primarily by transaction volume across a broad range of securities, asset classes and geographies. We avoid the risk of long or short positions in favor of earning small bid/ask spreads on large trading volumes across thousands of securities and other financial instruments.
By instantaneous hedging, I understand that they might be using strongly correlated products such as futures. However, what I do not understand is the fact that, if they aim at instantaneously hedging their position on ETF, they need to do a market order in the hedging product, hence paying the bid/ask spread there. Therefore, the previous paragraph only makes sense to me if the bid/ask spread of the future (for example) is smaller.
More precisely, continuing with the ETF shares and futures hedging example, the mentioned paragraph only makes sense to me if the following relation holds at least most of the time:
$$ETF_{Bid} \leq Future_{Bid} \leq Future_{Ask} \leq ETF_{Ask}$$
If this relation holds, and the market maker follows the following rule
1: If I buy the ETF at the bid price, I perform a market order to sell a future
2: If I sell the ETF at the ask price, I perform a market order to buy a future
then indeed the market maker is capable of locking returns. For example, if he buys an ETF share at time t=0 and sells it at time t=1, then \begin{align} P\&L(1) &= ETF_{Ask}(1) - ETF_{Bid}(0) + Future_{Bid}(0) - Future_{Ask}(1)\\ &= ETF_{Ask}(1) - ETF_{Bid}(1) - (Future_{Ask}(1) - Future_{Bid}(1)) + (ETF_{Bid}(1) - ETF_{Bid}(0)) - (Future_{Bid}(1)-Future_{Bid}(0)) \end{align} The first two terms represent the ETF Bid/Ask spread vs. the future Bid/Ask spread, whereas the second two terms gauge the hedging efficiency (HE)
Using the above-mentioned relation, it can be easily seen that
$$ETF_{Ask}(0) \geq + Future_{Bid}(0) \geq ETF_{Bid}(0)$$
$$-ETF_{Bid}(1) \geq -Future_{Bid}(1) \geq -ETF_{Ask}(1)$$
Hence,
$$ ETF_{Ask}(0) - ETF_{Bid}(0) \geq HE \geq -(ETF_{Ask}(1)-ETF_{Bid}(1))$$
Thus, assuming that the hedging efficiency is on average 0 (and, when different from 0, very small and little risky), under this hypothesis the market maker can only make profit on average and with little risk by instantaneous hedging techniques if the mention realtion holds.
I know this is an oversimplified example, but is this roughly how this instantaneous hedging thing works? I.e., using the fact that the hedging instrument has a tighter bid/ask spread.
If this is not the case, I would very much appreaciate a precise explanation/bibliography to understand what they exactly refer to.
Thanks in advance!