There is no thank you between equals.
Instead you have ‘that’s so kind of you’, ‘that’s awesome, I love it’, ‘I appreciate the gesture’, ‘I love it’, ‘I’m happy you cared about this’, ‘that’s huge, I can’t believe it. I love it’, etc.
In the upper class, thank you is something you receive from the other classes.
There is an adja proverb ‘a man does not say than you’.
Saying thank you is for people who are unlikely to reciprocate.