If I have an offer I’m going to accept, I should cancel all my additional scheduled callbacks, even if the firms have already booked my travel for them, correct?
Yes. Thank them and tell them that you’ve accepted an offer elsewhere.
Absolutely, the most expensive aspect of callbacks is not the travel expenses but lost attorney time. Nobody wants to interview somebody who has already decided to go elsewhere. That said things like hotel costs are probably refundable. They might have purchased refundable airfare as well.
OP. Got it, thanks. I grew up poor so was worried about all the sunk travel costs, but that makes sense.
Additional non-money point, but cancelling a callback could lead the firm to offer that callback to the next person down the list, so your classmates will be grateful.
I think this is the most important point