Is it usual? Yes. Most exchanges have tiered fee structures these days as well, and they are <0.1% in most cases for such high trading volume as well.
It's not like Huobi is losing any revenue from this, because before people can enter this VIP Program, they would have already earned a ton of commission from people trading at normal rates for the first 500-1000 BTC. Besides, the sheer amount of volume these traders generate mean that Huobi will be able to continue to make a ton of commission anyway.
If you think this is shady - it's not. It's just smart marketing, that is all.