Doesn't sound like too bad a deal to me. But I'd certainly start with a lower offer than what he's asking. Even if the two of ya agree on $50 less than his price, that's $50 ya got towards some add-ons for the Vulcan !!
And even if the splines haven't been checked for grease, they should still be in good condition with only that amount of miles. But be sure to make that one of your first maintenance chores !!
Hope ya stick around if ya do get it. Good luck