There's more to an item, especially one like a piece of clothing which involves design, than its utility value.
For a t-shirt, these things jump immediately to mind that may increase its cost:
- A limited batch
- A particular cut
- A particular print
- Supporting a clothing brand / designer you have a connection with
Why judge someone so harshly because they value some other aspect of the item differently than you? There's something incredibly ugly about being confident in your ignorance and casting judgement on other people.