Okay. So first, you tie one end,of a string to a doorknob...
Really, if this guy isn't a troll of some kind I'd be a tad surprised. Why post a plea for help for your animal on a financial website? I'm thinking he's enjoying the debate that's been started regarding the right to life for kitties.
I also think that any humane method of putting down the animal is acceptable, if it's necessary. Why spend a huge amount of money when you can do it yourself for far less money. I had a dog euthanized and cremated a couple years ago and it cost a few hundred dollars. She was 155 pounds, so didn't want to spend too much time digging a grave afterwards, so cremations is best for my big dogs. Anyway, it's not like I had her dig her own grave, but I did make the responsible decision to put her down (had cancer) and it wouldn't have mattered if I'd done it with a gun, a shot of something or electrocution, she is dead now, and I have missed her. Rural members of this forum understand that animals are animals. It's not murder to kill your cat for humane reasons. It is murder to kill someone else's cat, I guess, but i digress...
Op should go to a veterinary forum or blog. There's lots of debate over ways to inexpensively and humanely kill your pets on a number of websites and forums. Maybe this debate belongs here, or maybe it doesn't... Moderator should at least move it to the DIY board