I don't really consider any of my purchased boys 'rescues', however the one I got off of an abusive owner(Mandy) is definitely a rescue. I would have given that fish maybe a month to live, tops. They rarely fed him and never cleaned his water, but he was a fighter, and survived a long time in those conditions.
But I didn't pay a dime for him, I begged him off, however I still would consider him a rescue if I bought him because his permanent home was like that.
Betta in pets stores are not staying in those conditions long, they all sell or die eventually.
It's really the eyes that get me. They aren't like goldfish or guppies, these guys can speak to you if you are willing to watch them and listen.