Newegg.com offers Microsoft Office 365 Home 1 Year Product Key Card - 5 PC or 5 Mac [newegg.com]
for $71.09 after 10%-off promo code EMCRHBE23.
Office 365 comes with 1TB of OneDrive data for up to 5 users (for a total of 5TB). Given that competing services like Dropbox charge $100 a year for 1TB for 1 user, you're basically getting the same amount of storage for $29 less than Dropbox and they're throwing in the entire Office suite for free.
Alternatively, Amazon.com is selling Microsoft Office 365 for $78.99 [amazon.com]