I know it seems rather like sharp practice to us, but - and I've raised this point before - as an author, my feeling is that if Fred Bloggs is buying lots of copies of my book ("Viking Weapons & Warfare" - Tempus) and flogging them on at in inflated price, the best of luck to him. After all, that's what all retailers do, whether they are selling Aardvarks or Zebrite.
A further point is that publishing a book usually means learning more about the subject as people from all over will e-mail, phone & write with stuff that you didn't know before. This leads to revisions & more photos & thus to a Revised Edition. But no one in their right mind is going to issue a revised edition when the earlier one is still on the shelves, so the quicker they are gone, the better.
Stationary engine transfers are another thing I've seen sold in large numbers on eBay. Whilst they last a long time on the shelf, they do age & trying to apply an aged transfer can be frustrating in the extreme.
Lastly, an increase in sales volume means an increase in financial turnover and any profit can be more quickly turned into new projects & an ever expanding range.
Perhaps a better way of looking at it is, as enthusiasts, we get a discount ;o))
Regards,
Kim Siddorn