ONE CAKE per PERSON.
Went there on a Wednesday evening at 9pm. The lineup is crazy, but the time I left that place with 2 cakes in my bag, there were probably 20 people lined up behind me. Given that they only have 12 cakes available (freshly baked from oven) at a time, and it takes about 30 mins to get them ready... you can do the math and ask yourself if the cake is worth the wait.
With that said, personally I will still choose to wait and will definitely go again because the cake is that good (nothing else though). Uncle Tetsu is the ultimate one-trick pony that somehow will continue to be successful (but really think they can improve on their efficiency).