A large portion of the cost savings is by doing this yourself. If you want to have SC or anybody else get the parts for you please expect added costs. This is done out of the goodness of SC's heart since they could charge 699.99 EASILY and still be under the cost for most plates and other manifolds on the market.
If you do not want to put in the work to gather parts, i would advise you to check out EOS option. They have a full kit that also increases intake temps 30* after a pull for $1859.99. Its a great great product, i can say that. And another point, im sure we all have seen how the vendors suddenly dropped their prices on their PI kits. Odd to me that those have a $500+ markup huh?