I built a couple props last year (3 faceless ghouls - so basically some chicken wire, PVC, garbage bags & "shrouds") and some smaller Halloween stuff from Walmart (hanging skeleton, screeching cat skeleton, etc.). Back in July (middle of the long hot summer in Phoenix where I mostly don't go outside for 3 months - lots of "random thoughts time), I came up w/ the idea for a much larger scale setup featuring pirate skeletons, because I really enjoyed building my ghouls and the response I got from all the kids coming through (like 200 of them). Since I don't have a lot of "leftover stuff" or "last year's stuff" to work with, I had to start planning out what I was going to build and what else I needed to pull it off - including 7 5 foot skeletons, pirate clothes, a pile of foam board, paint, tape, etc. etc. etc., and then start shopping for this stuff. I've purchased nearly everything w/ attention to price, getting lots of scores at Goodwill, Michael's and the Dollar Store, but it's still adding up to probably $750 at this point, and still not complete. Not to mention I still have a crap ton of stuff I need to build, and it's just too hot to do things outside yet.
The plus side is that I can reuse some of this stuff - like the skeletons will always be useful, and the leftover building materials (scrap wood is one my most favorite things!) The other thing is the learning process - I regularly visit the Michael's, Hobby Lobby, Oriental Trading, and other retail websites w/ Halloween stuff so I know the going prices of most things. Then I cross check things against Walmart. But then I randomly stop into a dollar store (any variation - 99 cent store, Dollar Tree, Dollar General, etc.) and find a bunch of nearly the same stuff, maybe someone cheaper quality, but for huge % less. And then I go home and kick myself for not finding it sooner. But I'm learning ....!