I have never drunk Tieguanyin tea for 30 yuan a catty. If you say that a catty of Tieguanyin tea in 30 yuan is better than that in 70 yuan, I think it is possible, because 30 and 70 are the same grade of tea, and also because of the tea itself and your taste. I hope I can help you. /This website has a comprehensive introduction to Tieguanyin tea, so you can refer to it.