While sellers may well be legitimate, and abiding by the trading site's purchase codes, you have no way of telling who they are.
Prices are also very high.
Theatremonkey does not endorse buying from these sources. It does not sell tickets, and does not participate in any form of online auction. Please do however use the data on this site to make up your own mind about each deal. The box office number can be used for all events. Other numbers are often published for specific concerts, try them first, but you will reach the same general telephone room.