Former poster HairyKnuckles sheds some light on Billy Batts here:
http://www.gangsterbb.net/threads/ubbthreads.php?ubb=showflat&Number=797621&Searchpage=1&Main=25775&Words=%22william+bentvena%22&Search=true#Post797621

Hill says Batts "was with Johnny Gotti from near Fulton Street and he was hooked up with the Gambinos". We know Gotti wasn't made at this time so perhaps Hill just means he was part of the Fatico crew. Some researchers think that Batts wasn't even made.

I think Batts buying his button was just adlib on Pesci's part.