My costume is custom made and not something you can buy in one complete package. About the best Vader you can buy in a box, is the Rubies Supreme Edition Darth Vader costume for about $600-900. It is far from accurate and is poor quality in my opinion, but most people would still be impressed.
My helmet is made by Master Replicas and was pulled from the same mold they used in Episode III. There are a few to be had on eBay for a serious price. The leather suit I had custom made in Argentina. All of the armor pieces and chest box came from the Rubies costume, but I modified them with real metal parts, upgraded electronics, and automobile quality paint jobs. I also have a complete audio system for breathing and real voice quotes without any background noise. All together my final suit was about 2-3 years in the making and over $3,000.
