I'm not sure on the details of breeding betta, but when I was breeding my ADFs I started off with at least 100 tadpoles, and by the time they began to grow legs I had 12.
It doesn't make sense to me to breed fish if you can't find homes for the animals you produce. I'm not saying that you're a bad person for culling necessarily, but I wouldn't kill something because it's not pretty. It conflicts very sharply with my morals, even if it seems stupid to apply human morality to fish. I just don't have the guts to do something like that and feel okay about it afterwards.