Even $500 million may be difficult to sell to creditors as a good deal for them, in light of the appraisal by Christie’s, so celebration among art enthusiasts would be premature, said Michael Bennett, law professor at Northeastern University in Boston specializing in intellectual property and art law. The appraisal pegged 2,800 works at the DIA at between $454 million and $867 million. The appraisal considered only art works purchased for the museum with tax dollars.