I'm afraid I won't be able to contribute much to this discussion as I have yet to buy or sell materials (did it a few times in the beta but I won't count that).
But I think maybe there should be some discussion about what price to sell materials for at least as a base especially given the lack of an in game market to sell these items. This could help create personal updatable selling threads (I was considering this in the future). Along with easing the pain of wondering are you selling at a fair price.
Perhaps something by star level? Once again, I don't know much so these are just random numbers mostly. There's not much reasoning behind the numbers I've provided (if a consensus is reached later, I could try updating this post should I still be playing).
0 star - 100
1 star - 500
2 star - 1000
3 star - 2000
4 star - 3000
5 star - 10000
I'm aware some items would be worth more than others even in a particular star level (such as swordstone).
Now by all means, please discuss from your experiences if you deem this worthy of a discussion. Considering the game just started officially, this could be your chance to influence the future.
Another thread by someone else: http://forums.spiralknights.com/en/node/3777
Stars have little to do with rarity and usefulness.
To give a few examples:
Gel drops are 1*, but they are so abundant that nobody ever needs them. Current price: Ask a friend if you need some
Gremlin gizmos are 2*, but they are so abundant that nobody ever needs them. Current price: Ask a friend if you need some
Blue shards are 0*, abundant and useful. Current price: 50-100
Monster bones are 2*, somewhat rare, and quite usueful. Current price: 500-1000
Swordstones and Iron Gears are 2*, rarer, and quite useful. Current price: 1000-1500
Forbidden fruits are 2*, somewhat rare, but nobody needs them. Current price: ???
Flame souls are 5*, rare, but they can be farmed in Firestorm Citadel.
Trojan horseshoes are 5*, really rare, but only useful for crafting one weapon that few people use.
Sun silvers are 5*, really rare, useful, but you can get one from the token merchant now.