Perhaps in terms of actual item value, but if somebody puts in additional work or money to obtain more of X materials to make Y item to then sell it on for more profit then then this statement becomes false.
It's also worth noting that the item value is largely dependant on how it's valued by the market.
What you're looking at is capitalism.
I'd break down the rest of your points, but they already seem to have been addressed.
To further what Desu said - it's important that refinement has a negative yield to prevent inflation and stabilize the positive yield that production (catching) brings in (Notably of high value).