This is the email that I just received from Monoprice (I had sent them an email because I couldn't get audio to work with their cable and 2010 MBP):
Hello Josh,
I apologize for the inconvenience, but our cables are 1.1 VESA compliant and do not support audio. You need a 1.2 VESA compliant cable in order to pass audio. We currently do not carry any 1.2 VESA compliant cables. Thank you.
If you have any further questions please feel free to contact me.
Regards,
Jesus Alcala
Technical Support Specialist