Frankly I don't have a solution to offer either. The best I've suggested is looking very hard at the parcel system, because costs are root of the issue and that is all about available funds vs outlayed funds. From the general lack of comments on that I've seen I'll have to assume that my opinion there is either largely not shared or the whole issue is too unclear for much to be said about it.
I understand your point with the 'parcels' issue, but I don't see a clear solution that way, because:
- Gold in 4E, at least as originally conceived, is a resource in the game. In order for it to be a meaningful resource, the amount available has to be limited.
- If the game is not to succumb to significant 'power drift' as the PCs advance levels, resources that have any persistence at all must be tied to level.
- As a result of these things, giving extra treasure - whether it be as a reward for 'successful play' or as a bonus for using consumable items and rituals - either unbalances long-term play or effectively means consumables are cost-free.
It seems to me that the root of the problem is not the resource itself, but the fact that persistent advantages (magic items, boons, etc.) and consumable advantages (consumable items, rituals, martial practices, alchemy) share the same resource pool. The obvious remedy seems to me to be to either:
(a) add another resource and split the resources between the two things, or
(b) add an extra resource that is required in addition to gold for the permanent advantages, while leaving gold as a requirement for both.
I think (a) suffers from lack of any clear, fitting alternate resource from the game "canon", but maybe (b) could work if some specific, non-purchasable action or "trigger" could be found to be required as an "enabler" for the creation of a specific item? That might fix item "creation" - "purchase" of permanent advanatages would need some other solution. A skill challenge (and time) requirement to find them, perhaps? Or something linked to milestones and quests that is a longer-term resource, rather than short-term (like healing surges)? Maybe just make the "trigger" a purely meta resource that determines both the ability to create and the availability to buy items?
Whatever - I think an extra resource or two is inescapably required to fix both this and the related "item daily power" issue. The "solution" of "chucking it all into the DM's lap" that is "Item Rarity" I find just lazy, deleterious to the game and unsuccessful at fixing what needs fixing. Both items and consumables/rituals should remain player-controlled features, limited by resources supplied by the DM through play according to DMG guidelines, IMV.