Literary elites love to rep Shakespeare's vocabulary: across his entire corpus, he uses 28,829 words, suggesting he knew over 100,000 words and arguably had the largest vocabulary, ever.
I decided to compare this data point against the most famous artists in hip hop. I used each artist's first 35,000 lyrics. That way, prolific artists, such as Jay-Z, could be compared to newer artists, such as Drake.
As two points of reference, Daniels also counted the number of unique words in the first 5,000 used words from seven of Shakespeare's works and the number of uniques from the first 35,000 words of Herman Melville's Moby-Dick.
I'm not sure how much stock I would put into these literary comparisons though, because this is purely a keyword count. So "pimps", "pimp", "pimping", and "pimpin" count as four words in a vocabulary and I have a hunch that variants of a single word is more common in rap lyrics than in Shakespeare and Melville. Again, I'm guessing here.
That said, although there could be similar issues within the rapper comparisons, I bet the counts are more comparable.