You are forgetting the seam where it goes to sleep after a while when it’s not being used every few minutes, and needs to be reconnected while the customer is waiting. In a crowded convention hall full of thousands of other vendors doing the same thing.

Oh, and the seam where if you do get it to connect to your phone, you then have both your phone and the customer’s phone fighting to get a connection to a tower saturated by people sharing their con photos/videos, streaming, and trying to process credit card transactions. It’s bad enough with one phone trying to authorize the transaction.

Also the seam where it’s one more damn thing to run out of power when you are at a table with nowhere to plug in because you are not gonna be moving enough stuff to be worth paying a couple hundred extra for the power fees unless you are a small press with the work of a dozen or so creators on your table.