My brother and I built it, so just materials was the cost. It took us about 12 hours to build the box. We had to shape the wood to make it work, including filing down grooves for the seat brackets, and cutting slits for them to seat into the box. I'm selling the box with the subs for $350, and am waiting for a response from one person. If I don't hear back in the next couple of days, I was going to list it in the swap and sell forum. The price is with the two subs. They are Rockford Fosgate Audiophile subs. Older style sub, but they were made for small sealed enclosures. I used to run 8 of them in the back of my F-150 extended cab.
The only thing with the box is it will need re-carpeted. We ran low on carpet and had to piece the ends together, and over time it started to separate. Not sure what shipping is going to be as it is pretty heavy. All the wood is 3/4 MDF.