Here's an interesting article on this topic. It's about the Minnesota Twins, but my guess is it's generally applicable. read more
How the Twins' big bashers choose their bats. In general, players select bats and MLB teams pay for them, although some players may buy their own bats if they see a new type of bat they like and want to try it out. As long as a bat meets MLB specs ( Baseball bat), it can be used in games. read more