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Ten days after a major SIM card hacking incident shook South Korea’s telecom sector, SK Telecom continues to suffer both reputational and financial damage. With ongoing confusion at service centers and growing consumer frustration, the company has seen its market capitalization drop by nearly 1 trillion won, and tens of thousands of subscribers have left. Analysts estimate that one-off costs—including SIM card replacement and regulatory fines—could reach up to 200 billion won.

As of April 29, SK Telecom’s share price closed at 53,400 won, down more than 7% from 57,700 won on April 18, the day the hacking was revealed. Although the stock remained stable initially, fears of secondary damage and a shortage of SIM card inventory triggered steep declines starting April 28. Market capitalization fell from 12.39 trillion won to 11.43 trillion won in just over a week, dropping the company to 40th place by market cap.

“This reflects deepening concerns over the seriousness of the breach and the possibility of further fallout, despite public apologies and free SIM replacement offers,” said Kim Jung-chan, an analyst at Korea Investment & Securities.

Subscriber losses have surged. While daily net losses were previously under 200, SK Telecom saw 1,665 users leave on April 26. On April 28, the day the company began offering free SIM replacements, 34,132 users ported their numbers to other carriers, while only 8,729 new users signed up—indicating a net loss of over 20,000 subscribers in a single day. The real figure may be higher when including customers who switched to budget carriers.

To stem the outflow, SK Telecom has significantly increased smartphone subsidies. Over the weekend, some dealers reportedly offered high cash-back deals on Samsung’s new Galaxy S25 models.

The financial toll is expected to worsen. According to securities analysts, the total cost of replacing SIM cards for SK Telecom’s 25 million users could range from 75 to 125 billion won, based on per-unit costs of 3,000 to 5,000 won. As of 9 a.m. on April 29, 280,000 users had already swapped their SIM cards, and over 4 million had made reservations.

In addition, SK Telecom is expected to face hundreds of billions of won in fines. Science and ICT Minister Yoo Young-sang told lawmakers the company would “face appropriate penalties” for its one-day delay in reporting the breach to authorities.

Shinhan Investment analyst Kim Ah-ram said, “Assuming full replacement and penalties, the financial hit could range from 100 to 200 billion won. If the issue is contained at this level, the stock price may eventually recover.”