I'm just going to use undercovertourist prices in this post, which include tax, because they have good deals and are reputable.
Flex 5 park tickets are 337.52 and include 14 days at IOA, USO, WnW, SW, and Aquatica.
1 day park to park IOA/USO $151.64 (or 2 days $197.21, 3 days $208.39, 4 days...