Quibble; Why is Aura +80% + -30%?

[kirbwarrior]

I've thought about this some, especially in regards to Multiplicative Modifiers and Alternative Enhancements*, and I was just going to house rule Aura to being +50% and 'it includes Melee Attack', but I wasn't certain if that was actually the intent of if there is actually a reason the two are broken up, and now I'm not certain if using MM would have the Melee Attack be a part of Aura (making the cost +50%) or apply to the whole advantage (which, with no other modifiers, would bring the cost to x1.05).

*Having an attack that can either be a regular ranged attack or an aura or an emanating area would normally somehow require Emanation and Melee Attack, but for purposes of Selectivity and Alternative Enhancements I just added the limitation costs to the enhancement costs as a 'meta-enhancement'.

Thoughts? I've noticed that Multiplicative Modifiers are starting to look much more attractive for the magic system I'm making so that Affliction actually gets cheaper with limitations comparably and that limiting large enhancements doesn't seem like a silly way to save points (IA with Area Effect 4 and Costs FP is more expensive than if I applied the Costs FP directly to Area Effect!).