Mine opinion is that the whole inf grind is boring for most players, and a barrier to entry for new players. I'd seed the auction house with every enhancement at some low level. Maybe 1,000 inf for each enhancement that can be slotted before level 50, and 10,000 inf for each requiring level 50.
Think of it this way: for how many players is influence not an important part of gameplay? Influence just isn’t a thing for most long-time players. Because we either have a nest egg of influence we'll never deplete, or we engage in boring influence grinding as needed.
I think it’s better to just open up enhancements to be free or minimal cost.