Mark Cuban.REUTERS/Mike Blake Mark Cuban says he turned down the chance to invest in Uber at a $10 million valuation. Uber's market value has surged by over 9,000-fold since then to north of $90 billion. Cuban could have paid $250,000 for an Uber stake worth $2.3 billion today, all else being equal. Mark Cuban turned down the chance to invest in Uber at a valuation of no more than $10 million — just over 0.01% of the ride-hailing company's $91 billion market capitalization today.The "Shark Tank" star bemoaned the missed opportunity during a recent episode of "Hart to Heart," actor Kevin Hart's talk show.