Not everything is OP. 9 times outta 10, ppl just don't know the value, and are blinded by greed. But while there are a lot of Overpriced items, there are occasionally some Underpriced items as well. As far as explaining how Alchemy works, I recommend you read darkdeavers guide to alchemy.
http://wlodb.com/topics/4281
FutureShock Guild Leader of the Cancer Server.