Well, that's somewhat true in my case. BUT there are two big differences. 1.) The reason you're gonna have to try hard if you want a relationship with me is because I have almost no desire to be in a relationship, and you'd have to change my mind about that. 2.) I tell people up front that I'm not looking for a relationship. I don't drag people along with "maybes" so I can have a backup if I change my mind.
After that, it's your own fault if you chase me and are disappointed in the end result.
And as a side note, I know MANY people don't take "I'm not interested" at face value. No matter how many times you say it, they seem to think it means "try harder." XP