That's a good price, not cheap, but they seem to hold their value.
Front box was not an option until roughly 2011 onward on the MkIII.
Then some owners retro fitted the new box to their older trailers, had to be the longer A frame trailer.
2008 model is known as a MkII. and may have what's called a short or normal A frame.
The longer A frame was an option, I think 2008 on but could have been earlier.
There was an extension that track fitted to the short one which put extra (approx.) 500mm into the trailer A Frame length.
If you want the box, you have to give up on the frame for the jerrys.
There was also a battery in with the Jerrys and took up one of the spots.
I shifted my 2 Batteries to the rear of my Canning Tvan., similar to the latest model tvan.
Not only did it give me back spots for 2 Jerry's, but it improved the weight balance too.
If you purchased the box from Track it may not be as cheap as a custom built one.
Track Trailer owners have a web site you may like to visit.
http://www.tracktrailerforums.com/index.phpGood Luck.