I'm going to dispell some myths right now concerning the (non retina) MacBook Pro's maximum RAM upgrade. Apple only officially sells 8GB upgrades.
Since 2011, Sandy Bridge architecture allowed you to install up to 32GB depending on processor. Most of the processors had a max 16GB ram limit. It is supported by Intel's chipset.
Apple does not officially support it as well as many other manufactures. Since there are no dual 32Gb sticks, the most you can install is 16GB (2x 8GB sticks).
This holds true for the Ivy Bridge mid-2012 updates.
I have a mid 2012 i5-3210M MBP 13 running 16GB. The sticks are running DDR3 1600MHz (very fast RAM) and the total cost was $115. My other 16GB sticks running 1333 MHz can be as low as $80 discounted.
I have four or five Virtual Machines running concurrently without a sweat. With my M4 512GB SSD, starting Win8 preview and Win 7 with 4GB each is no problem.
Here are some picture proof. Apple may not officially support and sanction 16GB but it can run.