On-demand car service Uber is said to be in talks with investment firms to raise about $500 million at a $12 billion valuation, according to a report by the Wall Street Journal. That's even higher than the $10 billion valuation previously reported by Bloomberg. The start-up is reportedly planning to finalize the deal by the end of this quarter. It has already raised more than $400 million, counting Goldman Sachs and Google Ventures among its investors. Despite opposition from the taxi industry, the company has been expanding -- recently landing in Beijing, its 100th city. It's made deals with eBay's PayPal and the NFL and launched a courier delivery service in New York City, UberRUSH.