I do pretty intensely decorated, themed Halloween parties. Last one was a creepy carnival, with a midway games section, scavenger hunt and costume contest, and always with cash prizes but sometimes also include some pretty cool things like chocolate skulls, wine, movies, and games.
I build most everything myself using thrifted stuff, find by haunting (ha) craigslist, or stuff I find/scavenge at garage sales and trash days. I do spend a bit of money in the end, but it's a hobby I greatly enjoy and one of my few remaining creative outlets.
The neighborhood seems to love it too. We hand out good candy, to everyone (including young, old or no costume).
While we can afford this type of thing, it is really sad if someone is going "all out" and into debt to do so.