When you refine a raw resource, you can get any level (even yellow, just rare) resource from it.

When you deconstruct an item, the resources are 'capped' at the level of the item.
So breaking down a green, can give you a green resource but not a blue.

This is why so many people want to buy unprocessed rare resources, as there is a nice chance of getting a yellow resource from it when you process it. Processed stacks are useless.

Once I get a tradeskill to 50, I sell 'white' drops to the NPC, green drops I break down and sell the greens resources on the Market (90% of getting one per item broken down) and sell the blue and purple items on the guild store as is.

I buy stacks of raw resources and process them, and then resell the stack (normally just to the vendor for 400g) and sell the green, blue, and purple resource I get from processing them. The yellows I am saving until I get to V10 to make myself a nice set.

The fastest money maker at the moment, is going back to lower levels (they no longer drop loot or give exp but still will drop 'crafting materials' eg leather etc.)
AOE lots of mobs that drop medium armor parts, and processing theses in stacks to get yellow resources to sell.

I've seen clusters of bots doing this now, just running in a group around a loop and spamming the templar spear ability along a mudcrab shoreline area, all with random-letter names. They look like a training group running along the beach for fitness purposes.