James Levine costs the Boston Symphony. And he makes the musicians work hard. “The BSO players knew what they were getting into. That’s why they negotiated what’s called the ‘Levine Premium’ before the maestro’s first season. They get an extra $220 for each of the music director’s 12 weeks. With about 100 players in the BSO and including other expenses, the total adds up to roughly $278,000 for the season. And there are other costs…”