Here is a link to a website for Great War reenactors. It has additional links to companies that sell reproduction uniforms.
I don't know whether the price you were quoted is for a poorly made or well made hat but you need to keep in mind that whatever it is, it is not a mass produced item. The price you were quoted sounds as if it may be a lower quality hat, frankly. There is no market for selling hundreds of thousands of these so they tend to be made hand made, one by one, by specialty companies. The result is very high prices. If you want to be a Civil War or Great War or Revolutionary War, or Napoleonic war, or whatever war reenactor, you can pretty much plan on spending a minimum of $1,500 to $2,000 for a good quality reproduction full uniform with reproduction accoutrements. Those guys who go out on weekends and do reenacting are definitely not engaged in a low cost hobby.
http://www.reenactor.net/ww1/units_german.html