I can think of two reasons: (1) It was not his own company when the IRA made the investment. That is, the IRA invests alongside other investors at the founding. Anyone who wants to buy shares at 0.01 is able to do so. He is not dictating some special price that only he gets. (2) If some investors create an SPV to invest in PayPal (e.g. to limit liability), then his IRA becomes an investor in that SPV. He loses management control over that portion of the investment, but when the SPV sells its PayPal shares, it distributes the cash to all investors, including to the IRA.