Instead, the actual cost is the best foregone alternative — that is what one gave-up.
For example, if you spend $100 on shoes, and would instead have got a picture if the shoes had been unavailable, then the picture is the real cost of the shoes.
Or, for another example, one that many people don't like to see, if one for some reason spends $100 on an investment that will pay a 10% return, and otherwise would have used the $100 for an investment that pays a 12% return, then the cost of the $110 from the investment that one bought is $112, not the $100. Buying an investment that pays less that the best investment available means paying the cost of the foregone return. Buying the investment with the lower return brought a loss of $2.
When I read pieces that claim that Hostess was killed by ‘greedy capitalists’, I have to laugh. The ‘greedy capitalists’ didn't want to put their money into Hostess if they couldn't get at least the same rate of return that they could get elsewhere. The ‘greedy capitalists’ killed Hostess because they wouldn't subsidize Twinkies!
If all the people who buy into this ‘greedy capitalists’ theory would pool their own investment capital into a syndicate, then they'd have far more than enough money to buy all the relevant assets. It wouldn't make less sense for them to give-up investment income to get those Twinkies rollin' out the door than it would for the ‘greedy capitalists’ to do so. But I'm betting that they'll be too ‘greedy’.