The basis of valuation would depend on the type of cover being sought as per :
Insured own property– value agreed.
Sold item not delivered- selling price - fee commission.
Purchased item- cost price + fee/commission.
Property in Care Custody and Control-market value/liability, whichever is less.
Usually, the following % are used as Valuation for Dealers & Gallery owners.
Cost price + 20% or
Selling Price - 30%.
Fixation of SI would be at least the actual value of the property as agreed mutually above for private collectors and the highest value of the stock at any given point of time for Dealers and Gallery owners.