Ad title also seems a little misleading, it's not an "NSX Type-S Steering Wheel", it's a Momo Zagato - not an OEM Type S wheel (which I know is discontinued, but even if you find one brand new, is several hundred dollars cheaper than your asking price for this setup). Maybe add "Type S Style Wheel" to the title or something like that to clarify.
Your wheel is used, so let's take your $1000 Zagato wheel pricing (which in itself seems outrageously high, though since I own one of these too I'd love to be proven wrong and see some examples, all the better right...) and call that market value. An NSX-R Horn button set up with the horn rings and screws new is $295 shipped from theNSXshop. So you're essentially asking someone to pay $1000+ for just the Zagato horn button and box alone if I am reading your ad correctly? May as well just sell the horn and box separately... just a suggestion.