Stephen Bainbridge (UCLA) reports the rumor.  It strikes me as within the realm of the possible.  NYU is rumored–I emphasize rumored–to have paid 500K/year to dislodge one well-known scholar from a competitor school.  (NYU Philosophy is reported–this more reliably–to have paid 300K to dislodge a philosopher from a competitor.)  Non-salary compensation–housing or apartment subsidies, low-interest loans, tuition assistance, etc.–probably push more than a few law faculty into the 400K range.  But there is little reliable data on this, even from the state schools, where the compensation figures reported usually omit compensation from ‘private’ funding sources.