When you buy the full set of plans on the memory stick (why they don't have a secure download location is beyond me) it will include all the optional plans as well. Well worth the 10 + shipping they charge for it. I have made mental notes and a few written notes about certain ones. Such as OP-48 with regards to the AHRS bracket and not to rivet those rivets in the tailcone as I will simply have to remove them later.
As for the price of the spars, No idea. You are correct in the 1400 for the center section. I would be willing to guess somewhere in the neighborhood of 2500 each. The total wing kit is just over 10,000 so half is comprised of the spars. Makes sense to me as the other components are not that expensive. You can look up almost every part except for those using this "list".