Good news! From 1 April 2016, SQL Server 2014 Developer Edition is a free download if you’re a Visual Studio Dev Essentials member.
As a reminder, the Developer Edition includes the full feature set of the Enterprise Edition and is for development and testing only, and not for production environments or even for use with production data.
Here’s the Microsoft announcement (http://bit.ly/1NxiU83) where you’ll also find confirmation that SQL Server 2016 Developer Edition will also be free when it’s released in the next few months.