Sure you can kill someone in self defense fight with LRN bullet, but isn't someone you are killing deserve something better and fancier? After all it's the last thing he gets! :-)))
On the serious note, I don't understand OP concern with the cost of more expensive ammo. Yes, "fancier" bullets can be up to $2 per round or even more, but how many self defense situations are we getting into? Why can't someone use LRN on the range and then reload something more effective when gun goes on the night stand?