A couple years ago I dressed my whole family up in Pirate costumes for Halloween. I did it very cheaply, and easily made the costumes myself, which I prefer to buying a pre-made costume.
I went to a local thrift store on one of their 50% off days.
(Good Will has 50% off every other Saturday, and 40% off on Wednesday's - I actually prefer to go on Wednesday's, because they're not nearly as crowded as they are on Saturdays, and the prices are almost as good).
I bought button-down shirts and pants in varying colors, enough for everyone in the family, and a large colorful sheet.
I cut/ripped the sleeves off the shirts (put them over another, contrasting color shirt), cut the bottoms of the pants to make them ragged looking, and ripped up the sheet to give everyone a long sash tied around their waists. I probably spent less than $20 on everyone's costumes combined (I can't remember exactly).
Finally, Jack Sparrow style, we all wore bandana's, I put small, randomly placed braids in everyone's hair, (My husband had long hair at the time, so it worked well for him too), and I dug out my old gaudy jewelry from the 80's to share with everyone.
I am linking to Tip Junkie's Halloween Show and Tell!
We joined The Thrifty Home's penny pinching party! Check out all the great ideas, and add yours to the list!