Well for armor costs, it all depends on what quality armor you want. (You get what you pay for, No more, No less.(well... maybe less... but definitely not more)) So if you quickly throw together a suit out of cardboard and duct tape for a few dollars, it won't be as nice as you spend 1000+ dollars nicely sculpting and molding your parts.
The hard thing about deciding what method to use is to have an even balance of quality vs. price. As for me, I would do a nice pepakura suit because card stock is cheap and the only thing you would have to spend any real money on is finishing it.
