What is the fee to buy USDT?

Could you please explain to me, what exactly is the cost associated with purchasing USDT? I'm curious to know if there are any specific fees or charges that I should be aware of before making such a transaction. Is the fee a fixed amount or does it vary depending on certain factors? Also, are there any hidden costs or additional fees that might not be immediately apparent? It would be helpful if you could provide a comprehensive breakdown of all the associated expenses so that I can make an informed decision.