If the companies in question wanted to pay dividends out of those funds, they'd have to repatriate them into the US from the offshore holding companies & would

If the companies in question wanted to pay dividends out of those funds, they'd have to repatriate them into the US from the offshore holding companies & would inevitably incur US corporation tax on the resultant profits. So the cash only retains it's "full" value if the company can profitably invest it outside the US: if you think growth via R+D has peaked, then it's significantly less valuable! So how you choose to value the cash on hand depends very much on what you believe the future growth prospects of these companies via R+D or capital investment outside the US to be.