Folks seem to be mentally linking this news to Warren Buffett's comments about income tax disparity. Keep in mind that RSU's are taxed as earned income, valued on the day that they vest. Any appreciation above and beyond that would indeed be taxed at capital gains rates (15% if held longer than a year after vesting), but the core value will be taxed at his marginal rate of 35%.

Buffett's tax rate hovers around 15%, because the lion's share of his income comes from cap gains and qualified dividends. Cook will be paying more than double that on his income from this deal.