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There is a heatmap for you to choose best hours to make your transactions on chain, it does not apply for withdrawal fees.
https://gasfeesnow.com/heatmap/
You quoted enough websites, which I appreciate, but the Exchanges ones are just irrelevant to it because they will not use them. However, gasfeesnow.com is the most appropriate, and I checked it immediately then. It was about 7.9+ USDT more compared to what they wanted to charge, which makes it extortion. Or should I say the middle dealer they use was extorting.There is a heatmap for you to choose best hours to make your transactions on chain, it does not apply for withdrawal fees.
https://gasfeesnow.com/heatmap/
Exchanges generate revenue mainly from two things, one is trading fee and the other one is withdrawal fee so paying $8 fee is insane but that is the cost for the service, I am not backing the high withdrawal fee here just presenting the facts.
You don't even have to side with them, for that will amount to not having a point at all, the charge is outrageous and has no other name for that. I've never seen an exchange charging me more than 1 USDT to withdraw through BEP20, most of them charged far less. For almost a year now, Binance has been charging nothing for such transactions.That's certainly more inflated than what I've seen from other centralized custodial providers. I'm also surprised they lowered it for you. I would guess a lot of services out there would stand their ground instead and give canned answers lol—a lot go by the textbook. Perhaps your pitch was also good. 
That's why I love to use the best in the industry. And if we can't agree, why not move to another, after all, there are at least over 50 good ones I can move to.