What does it mean when some one says THIS IS PRICELESS?

Answer 1

When one says 'THIS IS PRICELESS', he means that the thing being referred to has no value.

Answer 2

When someone says "this is priceless," they are expressing that the thing or moment in question is extremely valuable and cannot be quantified with a price. It often indicates that the person views it as irreplaceable or of immense worth emotionally or sentimentally.