What does this mean and how can a piece of paper weigh twenty pounds?

The new screens were cast as single pieces, 7 by 15 feet, weighing about 1,500 pounds.

These pieces is four foot long, and weighs nearly as much as me.

The piece, which is priced at $75,000, is three feet tall and weighs 25 pounds.

The pieces have a bulky, heavy look, but weigh little.

The piece must have weighed two or three pounds.

Their disappearance was mysterious because each piece weighed more than 1,000 pounds.

How much do you think a piece one meter long would weigh?

This piece of huge size weighs around 2,000 kg.

The piece is made entirely of black granite and weighs about 300 tons.