By Julia Payne and Divya Rajagopal BRUSSELS/TORONTO (Reuters) -Group of Seven (G7) members and the European Union are considering price floors to promote rare earth production, as well as taxes on some Chinese exports to incentivise investment, four sources with knowledge of the discussions told Reuters. Rare earths are difficult-to-extract metallic elements critical to the manufacture of products including cell phones, cars and high-tech weapons. China, the world's leading producer of rare earths, surp ...