All of the northern teams benefit from the huge allocations given at both Preston and Burnley, about 5,500 and 7,500 respectively. Added to that some of them are no more than 15/20 minutes apart. We do not have the luxury of either of these things, with our closest game about 50 miles away and none of the southern allocations being above 2,000 (apart from Bristol City, which we sold out, and that's 85 miles away). Even Cardiff is way over 100 miles away.
We would have definitely sold the extra Leeds tickets. We sold out Plymouth, before it was postponed and re-arranged for midweek, midwinter, meaning we took about 1,000 fewer. Same with Burnley, where I think we would have either sold out, or been very close to it, if the original date hadn't been changed. Similarly Coventry on a Saturday, rather than Friday night on Sky, would have been about 1,000 more.
If you factor those four games in then I'd say you could add another 4,000 to our total following, or 175 to the average, putting it at about 1,750. Of course other clubs may be able to say something similar, although I'd be amazed if anyone else turned down extra tickets to a game that never even made general sale???!!!