2.What is the difference between the withdrawal fee and the on-chain transaction cost?
Everyone may be confused about this. In this case, the only difference between the withdrawal fee and the on-chain transaction cost is that the user hands the withdrawal fee to the exchange, then the exchange gives this withdrawal fee to the miners as an on-chain transaction cost, isn't it? Actually, the difference is more than that. The exchange does not just do a simple transfer of these fees.

Taking Bitcoin as an example, when a user initiates a transfer on the Bitcoin network, usually the user needs to pay a certain transfer fee to the miner.  The transfer fee is generally 0.0001 to 0.0015 BTC, but because the capacity of the block to accommodate the transaction record is limited, the miner preferentially packages transactions with high fees, so transactions with high fees can be confirmed faster. Especially in the case of block congestion, higher fees can greatly increase the probability of transaction being confirmed. Then the evaluation work falls to the exchange. The exchange can evaluate the network congestion of the blockchain network, and then pay the appropriate amount of processing fees to ensure that the users' withdrawals get packaged and confirmed as soon as possible. When the block is abnormally congested, it may be necessary to pay a fee several times higher than usual to ensure that the transaction is packaged and confirmed.

Therefore, the exchange eliminates the task of evaluating the status of the block for users, and users only needs to perform a few simple steps to complete withdraw, and the remaining complicated work can be left to the exchange.