Complex sentence: At a cost of about $70 per window, the total value of gold in the windows is over $1,000,000 but, due to the manufacturing technique used to make the glass, the gold is unrecoverable.
Split into simpler sentences: At a cost of about $70 per window, the total value of gold in the windows is over $1,000,000. But due to the manufacturing technique used to make the glass, the gold is unrecoverable.