I dont think these are error cards
These look like an overrun of the cards used in the signature series
I would think from a production point of view they would've printed all of the gold cards like this (even though all didn't have signature cards) as it would've been easier to just keep printing the original sheets
So if that is true i would say the unsigned sig cards of the cards that actually signed (Dunstall, Modra, Kernahan) might be quite rare as most would've been used for signature cards.
The others would've been quite plentiful at one point, as they would've had the same quantity printed but not had any signed ones
not sure on an actual value though as its unknown how many there actually are, maybe between $20 - $50 would be my guess?