What is the opportunity cost of attending a Kanye West concert of a free ticket to a Bon Jovi ticket which cost 40?

The opportunity cost of attending the Kanye West concert with a free ticket to the Bon Jovi concert is the value of what you forgo by not attending Bon Jovi. This includes the $40 cost of the ticket, as well as any potential enjoyment or experiences you would have had at that concert. Essentially, it's the total benefit you lose by choosing one concert over the other.