Back in 2008:
ICv2 - D&D 4E Back to Press
A WotC spokesperson has informed ICv2 that
Dungeons & Dragons 4th Edition has already gone back to press more than a week before its scheduled street date next Friday, June 6th. Sell-in of
4th Edition has “far exceeded expectations” and even though the initial print run for
4th Edition was 50% higher than the order for the previous
D&D 3.5 Edition, WotC has now realized that it is necessary to go back to press to meet anticipated reorder demand.
So, it was larger than the initial run of 3.5 in 2003. Is it reasonable to infer that had it been larger than the run of 3.0 they would have said that?
The problem is with returns - print runs are calculated on preorders by distributors. I know that the local Borders had an enormous pile of the first printing (second printing?) of 4e books - it sold well, but they over ordered, in part because they had been caught short by 3.5. Order 50, sell 20, return 30 does not help much. But they ordered that initial pile
expecting returns, I do not know if those initial returns were above expectations or not.
Those books probably did sell eventually - just not right away. Undamaged hardcovers can reenter the distribution stream. I am sure that WotC has cycled through several runs since - while it had, perhaps, a larger than expected number of returns, it was
still wildly successful. Stores often over order on what they expect to be big sellers, and the number sold was very impressive, just maybe not as enormous as they had hoped.
Later books have been somewhat less successful, not all of them, but there are some that just do not move at all.
Returns are the Devil. Some mainstream fiction might already have been remaindered if they had the kinds of returns I saw for 4e. (Christmas was bad. Very bad. I hate seeing covers torn off of paperback books for return.

)
So far Pathfinder seems to have avoided this, in part because their hardcover release schedule has been much more conservative than WotC's, back when 4e was new and shiny. And in part because Borders has not brought in 40 copies of the Core, but has been getting reasonable numbers and steadily selling through.
And PFRPG Core also sold through its initial, though much smaller, print run.
The Auld Grump