That would probably be the biggest hurdle to getting Samuel L. Jackson involved in John Wick.
Part of the film series’ success comes from the fact that they are comparatively inexpensive to produce.
Samuel L. Jackson can command some fairly big paydays, but if he’s willing to negotiate in order to get the role he wants, there’s no reason this couldn’t happen.
This especially works if the actor is willing to take a pay cut to do it.