It's always important, though, to look at these things with a healthy bit of skepticism and ask: is this bat really signed by Mickey Mantle? With sports memorabilia, it's almost impossible to tell absent personal knowledge. This particular seller notes that he doesn't have a certificate of authenticity—which is likely worth less than the paper it's printed on—and sufficiently alerts the seller to the possibility that it may not be a bona fide Mantle-signed bat.
But we do have plenty of examples of Mantle's fondness for working blue, especially with oral sex references. Given this history, one could reasonably assume that Mickey Mantle signed at least one bat "Merry Christmas cocksucker" and that this is such a bat. It's currently priced at $650.00 which is a pretty good deal, especially if you have the matching ball.