Valuation of collections is completed regularly in Australian museums, using a standardised methodology. See this publication by the Council of Australasian Museum Directors from 2018 https://camd.org.au/files/2018/11/CAMD-Collections-Valuation-Framework-1-Nov-2018.pdf
and general readership article https://www.intheblack.com/articles/2019/12/01/can-you-put-a-price-tag-on-heritage-assets
Valuation of scientific collections is often based on the ‘cost of recollecting’ - a contested methodology but used for practical purposes as there is often no market value (palaeontology and geology collections being the exception to this).
Museums are also often required to have at least a back of the envelope calculation of how many specimens / objects they hold. These numbers are often reported (at least in Australia) in Annual Reports published by the institution.
My point is that the data may already be collected by the institution but not added to the collection registry. Although making an assessment about whether valuations are comparable across varying methodologies, regularity of collecting the data, etc could make the inclusion of such figures dubious at best.