I recently bought a very thin and a very thick gaiwan in Yingge. Yesterday, I tested both and my regular thin gaiwan to see the influence on the taste of Bi Luo Chun, a Chinese green tea.
As expected, the most expensive gaiwan with the thinnest walls produced the best results. Why? The the tea cools down fastest in a pot with thin walls and the astringency/bitterness coming out at the end of the brew is not as strong as in a pot that retains the high heat. This really proved that thin walls are very important when it comes to green tea and flowery flavors.
What was more surprising was that my new expensive, nicely designed pitcher was giving inferior results compared to my cheap one. This time, the thinner walls of the pitcher had a negative impact on the tea: they let it cool down faster than the pitcher with preheated thick walls. The thin walls would only be an advantage if I were too lazy to preheat the pitcher, in which case the temperature drop would be less than in a pitcher with cold thick walls. So this is not a good gongfu cha tool!
Spending more does not always mean you get better tools for your tea. Especially in the realm of pottery, esthetics often takes precedence over function. Nobody will let you test the gaiwan or the teapot like one tests a car! All you can do is look at it (and maybe touch it, if the store allows). I'll give you another personal example soon.