You discovered a few important market dynamics! First is that the spot price is only one of the variables to take into consideration when trading. Market depth and liquidity are two others.
If someone says they will pay you $3 for an apple, you don't run out and buy 100 tons of apples. You first need to see how much they will pay for the second apple, the third apple, a ton of apples, 10 tons of apples, etc.
If someone says they will pay you $3 for an apple, you don't run out and buy 100 tons of apples. You first need to see how much they will pay for the second apple, the third apple, a ton of apples, 10 tons of apples, etc.