My bobby pins are only so-so quality, so they get bent out of shape pretty quickly. But honestly, even good bobby pins can be misshapen if your hair is thick enough and you're using them for up-dos.
I also tend to use bobby pins to "set" my bangs after I straighten them (basically, pin them off to the side for a bit so they keep their side-swept position all day). I often put the bobby pins in my pocket because I forget about them until I'm at work, which rubs off the finish and makes them look not great. And since I often use them on my bangs in a somewhat visible way, having not-great-looking bobby pins is not ideal.
I say just buy them, if you use bobby pins regularly. It's always better to have too many rather than too few. And even the good ones don't last forever.