Well, thank you very much Sir. But if X and Y addresses can be used to send funds in one transaction, how the transaction fees are calculated? Do you pay fees for each address sending funds? Or both addresses are combined in a single transaction and you pay a single fee?
You pay one single fee and the fee is based on your transaction's size.
Satoshi was referring that for better anonymity it's better to use different addresses for each input, and let's say, you had random ~100 inputs of micro-transactions to different addresses, and want to withdraw all of them on a different, single address? How it is being processed technically, do you pay fees as if you were sending Bitcoin from one address to another (X to Y)?
The more inputs, the bigger your transaction (size) will become, and that means higher fees. Avoid receiving micro-transactions payments (faucets, cloud mining platforms, etc.).
Read this for more details (technical):
https://bitcoin.stackexchange.com/questions/1195/how-to-calculate-transaction-size-before-sending-legacy-non-segwit-p2pkh-p2sh