Skullcandy, the American supplier of trendy headphones and T-shirts that are also sold in sporting goods stores, had a successful lunch of its initial public offering. The initial $20 price of its shares on the Nasdaq stock exchange valued the company at $535.6 million after reporting a 66.3 percent sales increase for the first quarter to $36.0 million, resulting in operating income of $3.9 million and net income of $1.1 million. The demand for the shares was so high that the opening price was raised by 11 percent and the number of shares to be sold by 13 percent to 9.44 million, representing a stake of 35.3 percent in the company. The share price rose as high as $23.40 in early trading on the first day before settling back to the opening price level.