Right, you could break the link by just making residuum cost 2 or 4 or 10x more than its nominal GP value equivalent, and then giving away some in treasures. You could probably also increase the yield from the Disenchant Item ritual somewhat at that point. I'd also rule that residuum doesn't work as a universal ingredient for all rituals, leave it as purely a substance used/required for items. You can basically have a 'law of conservation of residuum', the stuff simply cannot be created, though perhaps it can be destroyed... Mostly it gets lost! There could be processes for collecting environmentally dispersed residuum though, perhaps this is what dwarves do, mine it from deep underground in minute quantities.
I have a feeling about that, which is that 'redefining awesome' is a big part of what 4e GM's do. So, maybe it isn't really that much of a problemAlso my paradigm is tricky and relies on designer intuition too ie what exactly is "awesome"
Sounds very similar to some of the things I did without thinking too much about it... like giving away specific ingredients and residuum not working universally.. and situationally allowing gathering of ritual materia via skill challenges even. (another way to make rituals NOT be insta fixes).

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.