'A shekel' signifies the price or estimation of good and truth, and 'half a shekel' signifies the determination of the quantity thereof.

(References: Arcana Coelestia 3104)

6612. From all this it is also evident that the more external a person's thinking is, the less distance it spreads; and the more internal it is, the greater distance it spreads. For people whose thought is more external, that is, takes place on a sensory level, are in contact solely with the more obtuse spirits; but those whose thought is more internal, that is, springs from a rational level, are in contact with angels. The nature of the difference can be recognized from the closeness of the atmosphere in which sensory-minded spirits live and the freshness of the atmosphere in which the angels of heaven live. The difference between the two is like the difference between the transmission of sound and the transmission of light, a difference that students of natural phenomena are well acquainted with.