If Bitcoin price pumps from $1300 to $3000 in few hours, nobody would make profit from it, because the exchanges wouldn't allow you to sell your Bitcoins and make the fast profit, it would bring a big loss for exchange sites.
Do you agree with this?
What?
Why would the exchanges not allow for their users to sell their Bitcoins in the event of something like this? You almost never sell to the exchange itself, always to other people. If others are buying it for that value, then the exchange should just let it happen since it doesn't affect them.
Are you sure you know how most exchanges work? You're kind of making me think you think that you only ever sell to the exchange.