Check out the Discovery Store  Christmas in July sale-  DVD titles like Planet Earth: Pole to Pole, Mountains are only $1.99 or Orangutan Island Season 1 DVD Set- for only $4.99 (search under DVDs and sort by price)

You can also get $5 off $25 orders when you sign up for Discovery Store email (sign up at the top of page)

(Media shipping is only 2.95)