This is one of those ones where I see my self as being 80% right but I want to be fair because honestly I depend on my parents for a lot of stuff (rent, tuition, food, car insurance).
I also think this was a very normal mistake and my parents should give me enough room to make mistakes and learn from them.
edit: just for clarification I'm 20f.
Just picking out the parts that I think best illustrate that YTA. Top comment said it best though. Parents are paying your tuition, rent, food and you're blowing thousands of dollars to go to a anime convention, splurging to get the best room possible and going into debt? That's one hell of a slap in the face to your mom and dad.
YTA big time.