(Reuters) -Netflix added 18.9 million subscribers in its holiday quarter, blowing past Wall Street's forecasts, with live sporting events and the return of its popular South Korean series "Squid Game" attracting a record number of new customers, the company reported on Tuesday. The streaming giant said it will increase prices for most service plans in the U.S., Canada, Portugal and Argentina as it spends more on programming. Investors reacted enthusiastically to the results, sending Netflix's stock surging about 13% in extended trade, lifting its stock market value by almost $50 billion.