OK, obviously there are more than these two things, but these are definitely two of them. Why can't you have enough t-shirts and plastic cups? Each t-shirt and plastic cup captures a moment in your life and tells a story.
(Guys - use this excuse when your wife or girlfriend or both complain about the plastic cups in the cabinet and t-shirts in the closet.)
I wear t-shirts all year and most of my t-shirts tell some kind of story. They are stories are about where I picked up the shirts and what they meant at the time. For example, I have a Pac-Bell Park t-shirt that I bought in August 2001 during the Barry Bonds home run race. I went to games there on a Tuesday and Thursday and Bonds homered on the Monday and Wednesday (of course). Willie Mays was on the field on Thursday and it was great to see a legend like him in person and on the baseball field. The t-shirt reminds me of that trip, before baseball was intoxicated in PEDs, and before our country changed a few weeks later.
Yes the souvenir cups cost more at the game, but those things last forever! I use a Cincinnati Reds souvenir cup that I bought (full of diet coke at the time) with Ken Griffey Jr on it. In 2000, I bought it at the Cincinnati Reds opening day game. It was Griffey's first game in a Reds uniform and it was a rare Cincinnati home opener that was called for rain. The Reds tied the Brewers that wet afternoon 3-3. Junior was hitless in two at bats.
Keep your dignity and don't throw out those old cups and worn t-shirts! Keep them and bore someone with the story of when you bought them!