When I got my snakes the shipping price was for the delivery of the box, and it didn't matter how many snakes were in it, as long as they still fit. The box could hold a certain number of deli cups, one per snake, and that number was at least 8 (I don't quite remember). For hatchlings or young snakes all 7 would probably fit in one box, and your shipping costs would remain the same.
Congratulations on your expected additions to your household