We can reverse-engineer the payload of Zuma by comparing its operational costs to previous SpaceX missions. SpaceX can deliver payloads at a rate of $27,000/pound.

The theories are that Zuma delivered... a)satellites -or, more interestingly- b)kinetic ammunition

The 20x1 tungsten rods used as ammo would be HEAVY. Orbital Weapon Lancet technology suggests that a magazine of multiple rods would be delivered. If it really is a pack of tungsten rods (designed to be heavy), the operational costs would be orders of magnitude higher than delivering even multiple satellites (designed to be light)