Full skid package deal question

[delloro]

A "full skid package deal" for a 10-17 4Runner is $620. It includes three parts; the front skid ($220), a tranny skid ($165), and a xfer case skid ($235). But $220 + $165 + $235 = $620. What's the difference between buying each separately or buying the "deal"? Is something missing from the "deal" description?

Thanks