What is the halacha regarding the common custom of switching seats for an empty more expensive seat at a baseball or any other event? Thank you.
Once the seat has not been sold and will not be sold for that game, it is probably assumed that the seat may be taken by someone else who has paid to enter the arena. The seat grabber gains and the arena does not lose anything. I am however no expert on sporting events, and if in fact their policy is that this is forbidden and the seat must be purchased in any event, it would be forbidden to take the seat.