Q: Does having the Jade Statue mean you always get the maximum bonus no matter what Artifact you Sell or perform a Miracle with, or is it only the Jade Statue itself which gets this bonus?

A: It’s the Jade Statue which gets the bonus… not the player who owns it. The quality of always getting the full bonus only happens when you use the Jade Statue to do it. Possession of it does not confer this quality on the player when they use any other Artifact.