Aha! That's tricky... So, shall I hope for your brother to be particularly forgetful over the circumstances and associated instructions under which he was given the pair in the first place? What an unforeseen happenstance... =D
No. Not tricky at all - it may well meet a number of needs simultaneously.
They are excellent headphones and not much used.
Besides, we're adults and he will perfectly well know the cost of those headphones, at least, he will if he googles them; for a - fairly significant - birthday a few years ago, I gave him my old MBA (I needed a new one) and he was thrilled.
A bottle or two of good wine as well, and I'd imagine that we may be good to go.