still very new to this, but I do believe that I have a $25 pot that works to make oolong better. From the same vendor, I bought a different shape etc. pot (but it is still in the yixing category) that never has effected the taste of any tea one way or the other. From limited experience & from what I have gathered here, luck is as important as judgment & price in finding yixing that provides what one wants.
I also have one pot bought from gasninja that is fantastic for what I call "sweet" oolongs. I don't know how it was before he "seasoned" it, but I love it now.