I've found Queen Victoria issues in on-paper kiloware more than once, and I've been curious about this myself. I think Geoff's explanation is the likely one. In many countries, there are charities (church groups and the like) whose members save stamps on mail, aggregate it and sell it to dealers. That's how bulk lots of new issues come into being, for the most part. Older stamps will basically percolate through the system as individuals dispose of them in the manner that Geoff describes.
has a catalog value of $12.00, reported in italics in Scott designating it as a stamp that is difficult to value accurately (presumably because it's not appeared often enough in the market in recent years).
The italics are due to the fact that the stamp is valued higher in used condition than mint. In this case, the italics are a warning to watch out for fake cancels. In the case of that particular stamp, it may even be why it ended up in kiloware - it could have been a fraudulent cover and its owner at some point decided just to basically toss it. It could, of course, be a legitimate use, but there is a possibility it was just tossed for that reason.