Let's give an example of you bought 100 BTC at 9000$ Price and the price went 9010$ in seconds then you sold, so your profit will be 1000$, may 500$ fees, but the another 500$ you made it profit in seconds!
Let's discuss at the point!
That example clearly implies that the person investing is very rich. 100 Bitcoin at the current price is $1,000,000.
Therefore this man from your example is already rich even before he starts investing in cryptocurrency
Anyway, most of the people who thinks Bitcoin is a get rich quick scheme was left disappointed lol.
There's no short cut in earning good profit. That example ain't easy, you don't expect to sell that massive amount of Bitcoin all at the same time.