Actually, the library fine thing is a stress dream, not a bargain bin. My therapist explained that. The brain picks a small, fixable problem to stand in for bigger, scarier stress we're avoiding. So the 15 cent fine isn't about the book, it's your mind trying to process some other worry in a safe way. The milk dream is the same deal. It's not weird, it's just how brains try to handle stuff.
The milk thing is so specific it's creepy. My brain does that too, where it latches onto one tiny errand from three weeks ago and turns it into dream fuel. Last month I had a full nightmare about my library book being overdue. Not giant spiders, just a 15 cent fine. Our minds are weird little bargain bins sometimes.