Thank you for letting me know you could opt out of the (enormous) Mile High catalogues on their website. I just did it under the "Edit User Information" link here:
https://www.milehighcardco.com/EditUser.aspx
For Huggins and Scott, you can click where it says "Or you can GO GREEN and earn a ten dollar credit per auction when you win lots and do not receive a catalog" on the main page and it brings up a pop up screen where you can opt out (and receive a $10 credit towards purchases!) The link for the pop up is:
https://hugginsandscott.com/cgi-bin/vp.pl/nocat.htm