Capturing intelligent foes for profit

So after reading through lairs and encounters, I was really impressed by the thoroughness of the rules and procedures for extracting monster parts/horns/etc. for additional profit and use.

Then, there was a post in the main forums about a battle not big enough to justify using domains at war but still having mercenary participants, and how plunder would still be expected.

Now, as I recall, a good deal of the profit earned from going to war revolved around ransoming/selling to slavery the survivors of the enemy force for an average of 40gp per head.  Is this something that a party willing to delve into this sort of behavior be able to do?  Arguably, the effort expended of demanding surrender/taking foes alive without killing/maiming them would be very similar to the effort in not damaging monster parts.

Example: the party and a band of their henchmen and storm an orcish village that has been raiding the countryside.  When they're victorious, they obviously take all of the silver and trade goods, as well as the chieftain's magic +1 Axe, but could they reasonably round up the orcs who threw down their weapons/survived the mortal wound roll and do some combination of:
1) Ransoming them to another town of their tribe
2) Collecting bounties for particular cruel orcs back in town to be hung
3) Sell them to a rival clan of orcs, or perhaps an indenture period that the Auran empire considers acceptable that Alex has posted elsewhere.

Is this going to imbalance the game if a party decides this is a tack they want to take?  Is it too much money on top of the treasure the orcs would have, or is it justified by the additional difficulty of taking prisoners and risking escape/betrayal?

Assuming this is a valid strategy, I assume it's best to just go with the standard 40gp average? or should it be altered in some way?

Isn’t 40 gp the average for an adult human? I assume the value of a ransomed/enslaved intelligent monster would be the same as the cost of buying one as a slave, which is calculatable from Domains at War rules (I forget if it’s already on the tables, but as I recall, it’s a factor of their monthly wage, so it’s calculateable either way.)

Jard, I'll be providing gp values for humanoid slaves in Lairs & Encounters. The charts are blank right now in the sneak preview but they'll be detailed in the final product.

Players certainly can capture enemies and sell them into slavery. (In the ancient world this was considered more merciful than killing them.) 

ah, good old fashioned anitiquity mercy!  The Byzantiums were the most merciful of all "We don't want to KILL you, that wouldn't be christian. So instead we're going to blind and castrate you, as Jesus would have done." :-P

Well, earlier in antiquity you didn't ruin the potential value of a slave by blinding and castrating them. That's very particular to the Byzantines.