It makes me smile, all these rich people with expensive 5D3 cameras who don't want to pay for Canon batteries.
Not fair, dude.
First of all -it's a 6D, not a 5D3. And, everything adds up: lenses, tripod, backpacks, camera, accessories- it's not an unlimited well. Further to that- mortgages on two properties, 3 teenage kids getting ready for university, and, (not trying to elicit sympathy, just explaining budget constraints)- other expensive hobbies.
If I can (intelligently) save ten bucks- I'll do it. I'd rather give that 10 bucks to the Heart & Stroke lady than to Canon, especially when there's a perception (rightly or wrongly) that Canon's attempting to extort their customers through proprietary technology.