Doesn't appear to be much volume at all in this. Any ideas as to why. Shorting Gold / Long Silver or vice versa is just the way to go? Why do they keep these low-vol products around then? Curious.
Exchange legging mechanism / exchange guaranteed spreads, an additional source of revenues. The exchanges cost benefit determines if they keep the products listed. Download a volume EOD report or SPAN margin report you will see just how many of these there actually are.
Also, simply legging in/out of the spread is straightforward with both contracts – i.e., May ’20 Silver/June ’20 Gold – are liquid and for FCM’s applying SPAN requirements, any SPAN-determined reduction for the spread would be calculated for your account.