Stadium Events wasnt rare when it was released. It was re-released by Nintendo as World Class Track Meet. The unsold copies were returned and destroyed I think.
So I wouldnt say it was hard to find when it was released; it was there but nobody wanted it.
Super Mario 2 was very hard to find. I remember my dad took me to like 5 video game stores looking for it before we found one copy (the last one left), and it was 55$.
Also Urban Yeti was advertised & sold on television commercials, and I think it also had a (limited?) release in stores.
I wouldnt consider this one hard to get since it was easily bought if you had a phone and credit card.