Problem is Aeon is really good at dealing with significant groups of percies, and them being able to get those 5 meters for free pretty much makes it impossible to punish stupid aggressive ACUs with the tool that is supposed to be able to do it via land. Snipers don't have the problem, percies and bricks do.
Aeon Gun ACU
That's fair. I suppose I don't see that often at ~1400 range, as stupidly aggressive Coms tend to die to a combined Gunship & Strat attack.
@phong For what it's worth I'm learning some stuff by reading the arguments provided. 
I was also not happy with the cost of the additional 5 meters, but then I remembered that I use Aeon ACU as a mobile defensive overcharge turret hiding under shields late game dealing up to 15k damage to land units from 35 units away (colossus is 40), and... whatever, let it be. Additional testing will show if that's the proper cost.