I don't fully understand the appeal myself. It's basically just finger-tops, so there is no real tricks you can do with them like you can with a regular spin-top that you throw with a string. Just spin and wait watch. I even wonder about the geographical breakdown of sales. Do they sell better in Colorado, California, and Oregon? Something to do after you smoked one and the pizza isn't quite ready?
More seriously, I can't criticize too much as I have my share of trophies and prizes from minor yo-yo and spin-top contests from earlier in my life. You can spend too much on yo-yos seeking better performance (and I have), but that is in the quest to be able to do more tricks. I even know one of the customers where I service office equipment has a sizeable collection of finger tops, but mostly of the wood and plastic variety. I have not seen any of these brass/bronze/aluminium tops on his desk. I have offered to teach him how to throw a real spin-top sometime.