The phrase "inestimable value" means something is extremely valuable or priceless. It cannot be measured or quantified accurately because it holds immense worth or importance. Full definition
Together with interested members of his congregation, the clergyman could be of inestimable value in personal as well as group counseling during their difficult period of loss and aloneness. (religion-online.org)
After the war Eisenhower wrote: «Throughout France the Resistance had been of inestimable value in the campaign. (bookbrowse.com)
Living in a foreign country not only gives you a deep understanding of another culture, it introduces you to new ways of being and seeing that are of inestimable value on later journeys. (worldhum.com)