Sales at Elon Musk’s X jumped during the third quarter, but the social network is still dealing with significant costs — including from the firm’s restructuring — as the billionaire works to turn around the business he bought for $44 billion. The company, formerly known as Twitter, reported $752 million in revenue in the three-month period ended Sept. 30, a jump of more than 17% from the same period one year prior, according to people briefed on the numbers who declined to be identified as the d...