I started building an Indiana Jones costume when I was kid back in the 80s. It wasn't until 2001 that I got serious about it and started finding detailed pieces and spending way too much money. Needless to say, this created a desire to build other costumes as well that are all works in progress.
My inspiration really came from Raiders of the Lost Ark. Despite having watched all the movies many times over the years, I realized that Raiders is my favorite, both as a movie, and the costume.
The costume as it currently stands took about 5 years to assemble. I started with small pieces and built up slowly. I think that the last estimate I ran for someone on the cost was over $2000. That doesn't include the multiple versions of the various pieces I tested out, that's just the price tag for the pieces that made it.
My tips for others would be to use the years of research at Indygear.com to help guide you in your purchases. Part of the reason it took so long for me to assemble my costume was the cost, but the main part was ensuring that I bought the right pieces.
Here are three photos. I realized as I looked for pictures to post in this thread, I don't have any good pictures of the ensemble; I might have to work to fix that. The first is of me in Nov 2005; I am wearing a borrowed hat and my first jacket. Following that, I flushed out the entire costume with a new hat and a bespoke jacket. The next two are the complete costume in Nov 2008. These are the last two pictures taken of the entire costume. Just a couple hours after these pictures were taken, my jacket was stolen. I've since purchased a replacement, but I'm no where near as happy with it.