Rocket girl .. Two liter rockets, construction paper flames, duct tape harness.
The year my middle daughter wanted to be her dad. We own a loghome company and dad is accident prone. LOL dollar store items, dolled up with fake crow bar through the noggin and blood . and dad's tool belt.
Killer doll .. Wig made out of yarn. Again dollar store ax.
You can get tons of inexpensive costume pieces at thrift stores this time of year. I bought some very cheap items for my own costume this year. For example, I just bought a brand new with tags, originally $20, layered capelet for only $3.99 at Goodwill last weekend. Bought a 50's type tea length party dress, too, for about $6. Made myself a broom with a pine branch that I sanded and stained and the bristles for it I bought at Joann Fabrics on clearance for under a dollar. With a few other pieces I got for cheap on ebay, or already had at home, I'm putting together and awesome party witch costume. For kids sized items, they would probably be even cheaper!
Oh, I don't have pics, but I also did a scarecrow costume for myself one year...pretty much for free with items around the house. Put colorful patches on an old pair of jeans, flannel/plaid shirt, pulled my hair into pigtails and crimped it to look like straw, khaki fisherman's hat, boots, gloves, stuck a corn cob in my front shirt pocket, added yellow yarn pieces out of my shirt sleeves and pant legs (or you can use corn husks/straw/yellow or tan strips of material/ect...whatever you have.) and then I painted my face with stitches around the mouth, eyes and nose with eyeliner and filled in the nose with red lip liner inside the stitches. I made it in 45 minutes, lol.
I did the same for my mom last year...she used an old straw hat, though, and tied a rope around her waist, too. I made her two felt crows...one for on her hat and one for in her front pocket, with some fall leaves. Also super cute and free!!