There are lots of special at Sanity on hundreds of DVDs, Blu-Rays and CDs, I've picked this because I haven't seen Vikings... :D
Each of the seasons sell for $29.99, but getting all 3 of them on DVD would only cost you $50. The boxset sells for $89.25 at JB Hi-Fi or if you get the seasons individually you would be paying over $90 not only at JB Hi-Fi, but Big W, Zavvi and ABC as well (amongst other stores).
They've also got Arrow, Game of Thrones, Downton Abbey, Orange Is The New Black, House of Cards, Gotham in the collection of just over 800 titles in the "3 for $50" sale section.
Available online only until Monday, the 26th of September.