@Arkandel
So when applying for the same thing - let's say a 5-dot Gadget - with the same mechanical goal in mind ('I want to punch harder') I might end up with a bonus ('+5 to punchery!') while shameless jerks like @HelloRaptor end up with something far better ('+5 to punchery and 50% chance for a knockout! and it projects a WHAP! sound balloon over the target's head!') simply because the rules for what's permitted are fuzzy and there aren't samples to go by and determine how much power each dot level represents. There are a few in the splat-books usually but the pool is tiny and MUSHes often interpret then set the bar differently.
That's not really the case for Mage Legacies, though. There are a fuck ton of them. There are two entire books full of them, and more in every Order book, etc. Here's a list. They do vary pretty wildly in power level, from the barely useful to the earth shatteringly ridiculous, but there's no shortage of examples to pull from or base ideas on.
As for you being opposed to asking for more bang for your buck, that's a pretty poor excuse for anything, man.
It only gets worse if people expect theirs to be exclusive because some of the nicer mechanics (reflexive healing, damage downgrade/upgrade, etc) really are few in number.
Again, I'm only speaking of Mage Legacies, but exclusive is a weird way to put it. While I can only speak for myself, the situation wasn't even exclusive, it was that my character had developed his Legacy IC and it was not a Legacy people were walking around teaching in the wider world, so somebody suddenly showing up claiming otherwise was pretty disgruntling.
I know that I, along with a couple of others in similar situations, was more than happy to bring someone into the Legacy. The problem was that people wanted to bring in brand new characters who already had it, and then got pissy when told that wasn't cool. Or in one case was told it was cool by an asshole staffer who I still think new better.
And since you're focused on specific powers, the folks I spoke to with other custom legacies couldn't have given two fucks if somebody used their shit as the basis for something new. Want reflexive healing or damage downgrading? Cool, come up with your own spin on it. Every power my Legacy had was directly based on shit I found just poking around the Legacies. Want to make something more powerful in one area, weaken it in another, etc. Slap a new coat of paint on it, there you go.
People objecting to other folks being allowed access to their custom Legacy, one created IC, isn't about coveting a particular power. As I said before, I found people trying to claim that because they came up with a spell nobody else should be able to cast it to be pretty lame. But whining because you don't get to come in as an established Superdude Legacy character when Dude is the one who created the Superdude Legacy IC and hasn't had a chance to bring anybody else into it, is not even remotely the same thing.
Now, I did hear that at one point there was a kerfluffle because a player had designed an existing Legacy for his character to be a part of and was getting pissy over people wanting to bring in characters who also belonged to it. That, again, isn't even remotely the same thing. He was a douche for trying to assert that because he'd come up with it OOC nobody else could use it, when his having bought it at straight Gnosis (and the Legacy writeup itself) indicated there were NPCs out there with that Legacy.
reflexive healing
This has been mentioned more than once, and I grind my teeth at people using it an example of overpowered Legacy powers. Yes, it was reflexive healing. With a limit of no more than base Stamina+Size healing per day, that could only be activated immediately after taking damage (so if you took 5 but only rolled 2 succs, you don't get to try and heal the other 3 until you've been injured again, at which point there's even more damage to heal).
The Legacy healing power it was based on wasn't reflexive but was otherwise Disbelief-free healing all day if you needed it. What's functionally an extra 7-11 HL per day is really only situationally better than 'however many that you need', especially when there was a Life spell to just give yourself extra health levels and another for flat out regeneration.