Again, the kingdom of Heaven is like treasure hidden in a field, which a man found and hid; and for joy over it he goes and sells all that he has and buys that field.matt 13:44
The kingdom of heaven is beyond what money can buy. Buy it is hidden. This means that for a passer-by or a casual seeker, it is invisible. Eternal things are invisible to the natural eye, yet it is a treasure of a great price.