@Blown
I was more referring to the secondary ticket market. I would be very careful of buying outside the arena because you have no assurance of real tickets, as @mayjay correctly points out. Plus, when paying with cash, if you’re out the money, there’s not a lot you can do to get that money back.
The third party sites offer guarantees, and most credit cards also have fraud protection against fake tickets, so you’re in good shape to not lose any money if you buy from a site vs. buying from a stranger outside the arena.