I generally find it easier to get rid of plants if I have gotten into a bad mood. I guess I take my ire out on the plants. Whereas they were still in the garden because I was forgiving, or hated to destroy them, or was just plain procrastinating (maybe giving them a second chance), once my anger has gotten worked up, my bad mood makes it quite easy to say "You're Fired!"
It also helps if you are out of garden space, and you have some new and beautiful plant that you absolutely have to have room for. Make the comparison... I guarantee you that the new and beautiful plant will win every time.
If it helps you any, if you think the plant might be nice or appreciated in someone else's garden (it's not an utterly horrible plant), then you could always pot the plant and put it out on your street (or some random busy street corner) with a sign "Free Plant" (in small letters say what it is). The plant doesn't die (at your hands, anyway) and maybe someone in need (of flowers in their garden) gets a plant that they can appreciate. You will have done a Good Deed.
You mentioned money... I don't even want to think about the money I have spent on plants of all stripes, many of which are no longer here. You have to let go of that... the cost of the plants is irrelevant. What is important is that you are continually learning about gardening, and which plants please you (and which don't), and which plants can survive and thrive in your conditions (and which don't), and your garden is continually improving in tandem from these lessons. You can therefore think of the cost as a gardening tuition of sorts. (That, or you can think of it as an analog to the old saw about boats. "A boat is a hole in the water into which you pour money" becomes "A garden is a hole in the ground into which you pour money." In either case, the point being that some pleasures have an ongoing cost.)
I've gotten rid of tons of daylilies for varying reasons. (And to think I once wondered why people redid their daylily gardens every 2-3 years!
) I've lost count of the number of "nice enough but I have too many or I'm tired of it" daylilies I've given away to various people - but yes, there were also a lot of plants just plain thrown out (for rust susceptibility, or ugly flowers, or too few blooms, or whatever reason). It may have almost killed me the first few times I did it, but it does get easier... (Not
easy, mind you. Lots of marginal plants are still hanging around here, when I should have long since given them the boot.)
In that vein, we just dug up 5 clumps of daylilies yesterday. Two were tossed due to ugly flowers or rust susceptibility, but I told my garden helpers they could have the others. I don't know if they took them home with them, or not. By now, their gardens must be full of daylilies... (Sometimes I wonder if they take the plants and sell them at garage sales.
) Later this week, we will be planting the area with some
Cuphea, bearded irises, maybe a couple of the potted daylilies, and maybe I can squeeze an azalea in there in the shadiest part of the bed.
In short, I see these daylily removals as improving the garden... and hang the cost.
...So go and improve
yours! 
