the total cost is roughly $100-200 for the ITBS, shoot you might be able to get them a junk yard ya know, the horns cost around $25-$30 a piece, the filter cost $89, and the brackets to hold the filter cost $25 ( you need 2 of them),

that picture i got from honda tech, my buddy has a set that looks very similar to those, he got the whole set up used for $300