Yeah there will also be ways to convert lower level materials into higher ones, there may even be certain crafts that fail or end up spending more materials than expected to finish based on crafter skill, etc. Plenty of sinks so to speak.
Also some crafts that are a bit more random and out of a crafters control of what lays behind the magical boxes created.
Well, it all makes sense! Those systems should also help to stabilize prices and create demand for lower-tier materials, this could definitely keep the market healthy. I am looking forward to see how it all comes together in practice.