Today only, the Discovery Channel Store is offering both DVD sets together for the ridiculously low price of $47.99 (a savings of 70%!). By comparison, Planet Earth on its own sells for $49.99 at the store.
To take advantage of this offer (which does not appear to be advertised on the website), enter promo code EARTHEML at checkout.
Additionally, take another 25% off items in the stores Earth Day section. (Click on the link to go directly there.) Enter promo code EARTHDAY to get this discount.
Both offers are only available today!