When it comes to signatures, I don't get them very often, and keep it to my own photography. When a pic is worthy of being enlarged to poster size, then I chase the relevant signatures and they do not get sold. Never yet had to pay for a signature. Had a good run at the 2014 12 Hour getting all the signatures I wanted on earlier pics, plus a decade earlier got all 4 drivers + Garry Rogers on a pic of the first B24 winning Monaro. Don't have Mr Moffat's autograph, but that's because he stopped racing before I started taking decent pics. Brocky lives on in a pic from the '95 AGP event.
https://1drv.ms/i/s!Aj95AhorJw08jGCTamdJexbQ6x4q