Licensing SQL Server 2012 Standard Edition for development and test severs
There is certainly an economical way to do this - get an MSDN subscription. The licenses that you get allow you to use the software specifically in development and test environments. It looks like currently $1,199 would cover your needs for SQL Server (and assuming you can make use of some of the other software too), but you could always invest more to get additional software:

https://msdn.microsoft.com/en-US/subscriptions/buy/buy.aspx

Also, we've been asking for the ability to tell Developer Edition what our target edition is for ages. Please vote and comment on these items, explaining your use case and what you have to do to get around the problem:

http://connect.microsoft.com/SQLServer/feedback/details/496380/enable-sql-developer-edition-to-target-specific-sql-version

http://connect.microsoft.com/SQLServer/feedback/details/664953/target-platforms-by-allowing-disabling-features-in-developer-edition

http://connect.microsoft.com/SQLServer/feedback/details/507277/allow-developer-edition-to-emulate-feature-set-of-different-editions

http://connect.microsoft.com/SQLServer/feedback/details/420180/implement-a-configuration-option-that-allows-a-sql-server-developer-edition-instance-to-behave-as-a-standard-edition-instance

http://connect.microsoft.com/SQLServer/feedback/details/331297/developer-edition-in-standard-workgroup-mode

http://connect.microsoft.com/SQLServer/feedback/details/125239/edition-compatability-level-in-developer-edition

The more comments, the better!

This feature should also make it into SSDT at some point. But they're only going to do it if there is enough customer noise about it. :-)