Ha! I guess I'm a serial killer. I'm ruthless about culling--and 100% of my plants are plants I've paid for. I look at it this way---I may not keep the plant, but I've learned something from it:
1) I can't grow it
2) I don't like it (the blooms or the plant)
3) I won't make the same mistake again.
4) I like other plants much, much more
5) I have too many to properly take care of.
6) It takes too much time and thus not for me.
So I throw out or give it away. I've thrown out healhty plants because I can't find someone to give them to, and I've thrown out sickly/dead plants too.
I really don't feel guilty about it--I take it as a learning experience.