You're on an exchange. Bitcoin is showing a price of $65,432. You tap buy. You assume you're getting Bitcoin at $65,432.
You're not.
The price you see on screen is a lie. Or more accurately, it's only part of the truth. That number is the last traded price, what the most recent buyer paid. It says nothing about what YOU'll pay when you hit buy. That depends on something most beginners never look at: the order book.…