Ok, I have come up with a workaround for my problem with the queue, but please let me know if you think it will cause major problems!
When something comes up that isn't listed in the Marketplace, I enter a value of 999,999 for it. To avoid skewing the dataset overall, though, at the end of each session of using the queue I go down my "Your Submissions" list and open each item with a value of 999,999 and remove that value from the item.
I experimented a bit, and if I remove the value immediately the item goes back into the pool of "50 items that have gone the longest without updates" so to be able to skip them entirely I have to leave a placeholder price in place until I am done entering other data. One benefit to this however is that it means that my placeholder prices don't cause the system to think that the item has been updated recently, so it will still show up in the queue for others after I am done, and will still get priority (assuming a listing does appear in the marketplace!)