“The more you invest in me, the more I’ll put out,” was not what Harper Moen meant to say when she met with the CEO of RunFit, a sportswear company. She tried to correct herself, “I mean, I’ll have better chances to win more matches.” The burgeoning tennis star has a decent coach, but she sought upgrades to the rest of her staff to excel and reach her full potential. RunFit had offered her only a handful of cash a year, a...