Ha, an update.
When I originally queried this, the book was listed at $17.47, with no discount.
So, I emailed DriveThruRPG about this, asking if it was intentional that the original Battlefield Evolution was not being included in the discount of all Mongoose products, or had just slipped through the net.
And now, it's being listed at $14.99 - a reduction from the "normal" price of $24.99!
I'm sorry, this is just not right - it was never at $24.99 and to claim that this is the price before the reduction is just blatant lying.
Hmmmm. I think that with shady practices such as this, I will not be ordering anything from DriveThruRPG.