I've done some more research since my original post. Here are my thoughts:
The RAM that OWC is selling works fine in the new (2012) Macbook Pro (I bought the 8G kit and installed it--no problems). The RAM spec sheet says it is 1.35V which is the new 22nm DDR3L format.
DDR3L is required by the industry spec to work at 1.5V, so even if your computer was designed for DDR3 (any mac made before June, 2012), it would work with DDR3L too, but use more power assuming the 1600MHz parts work in 1333MHz machines (according to user testimonials at Newegg, they do work.)
The new Macbook pro is Ivy Bridge/22nm IC process node--same as DDR3L. So I'm guessing that means the 2012 Macbook pro provides a 1.35V power supply for the memory which would imply 1.5V (regular DDR3) will actually *not* work--or at least not reliably. This is one of those situations where folks might experiment with certain brands of 1.5V memory and discover that it works in the 2012 MBP. However, it appears to be too early for those folks to have tried it yet and see if doing so stands the test of time.
Even if the 2012 Macbook pro can use 1.5V memory, it doesn't save you that much money and the 1.35V parts use 40% less power which in a laptop is very beneficial especially if you're going to 8G or 16G parts. I paid $60 for 8G. I saw 1.5V parts for $40 at the cheapest at newegg. Not enough savings to risk it not working and consuming a lot more power (shorter battery life, hotter operation...) There aren't any user reviews regarding compatibility with 2012 MBP at Newegg, so I consider buying from them is too risky until braver souls have tried them.
Older Macbook Pros (1.5V), will save about 20% power running the DDR3L parts at 1.5V, so even those machines benefit from using DDR3L. I've read some user testimonials that older macbook pros can run memory at 1600MHz which means they'd run even hotter which is even more reason to get DDR3L parts.
The DRAM is sort of close to the battery in the Macbook Pros and you don't want something hot being near the battery because it'll shorten the service life of the battery. Again, get the DDR3L parts if possible.
The main reason memory for the new Macbook pro would be more expensive is not the voltage--it's the speed. 1600MHz memory is simply more expensive than 1333MHz memory, regardless of voltage. Still, I haven't seen anything like 80% difference between them for 8G or 16G kits--more like 20% or even less. In a few months, I bet there'll be no difference in price.
Hope that helps.
Bart