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I don't understand the part about market makers benefiting from wide spreads. Can you explain that a bit more?
Let me attempt to clarify this a little for you in the simplest of terms, because, to be honest, we are both noobs actually.
As I understood this, a wider spread could actually mean a bigger profit. For example, if the bid (buy) price of BTC is at $6,000 and the ask (sell) price is $6,500, you could potentially make $500 in a single bid/ask or trade filled. That's $500 gain per BTC. If you are putting 10 BTC in there, that would be $5,000 for you. Compare it with a very narrow spread. Let's say, the bid is at $6,000 and the ask is at $6,100. There is only $100 as a potential profit per bid/ask.
This could help more:
https://www.investopedia.com/terms/m/marketmakerspread.aspFor example, market maker MM in a stock – let’s call it Alpha – may show a bid and ask price of $10 / $10.05, which means that MM is willing to buy it at $10 and sell it at $10.05. The spread of 5 cents is its profit per share traded. If MM can trade 10,000 shares at the posted bid and ask, its profit from the spread would be $500.