Sorry for the delay in my response. What size Flat-rate USPS box are you interested in? The small costs $7.20, the medium costs $15.50, and the large $18.90.
How many straight sections would you like? I think 8 or so would fit in a small box.
I suggest you look at the boxes online or at your PO and see which you would like to use ( and check the cost with them). The 13100 is an X shaped crossing and goes for $30, and each straight section for is $8. Add the track prices and the shipping cost and that would be your total. Let me know how/if you want to proceed.