They are still insisting, as they must, that each insured carry his weight by insuring to value; but for the wise buyer who will take the time to determine the correct value of his property (whether on a replacement cost or actual cash value basis) and purchase the appropriate amount of insurance, carriers will eliminate the co-insurance clause and add instead an "agreed amount clause".
There is no additional charge for the agreed amount clause - you simply have to purchase and pay for the proper amount of coverage.