By Katie Paul and Krystal Hu (Reuters) -Elon Musk suggested that a lower price for Twitter Inc may be appropriate as he and CEO Parag Agrawal quarreled over the company’s estimates of spam accounts on Monday, according to an attendee at a private conference where Musk was speaking. Twitter shares extended losses in late afternoon trading following Musk’s comments, which came at a conference in Miami that was closed to the press. Shares dropped more than 8% to close at $37.39, lower than their level the day before Musk revealed his Twitter stake in early April, sowing doubts that the billionair…