I have recently been wondering about the costs of deploying batallion and larger sized mercenaries to other nations, and considering what to charge them. Simply put, the costs are staggering, but I can't conceive of what they would be. Does anyone know what the monthly cost would be of deploying a batallion, including wages, and supplies?

Combat pay, I'm not quite sure about. I think it's around a 20% increase.

Supplies, well. That's far more complex. Are you going to import the luxuries of your homeland wholesale (air conditioning for tents, McFood), or are you going to rely on a big pot of stew?

Much of the costs for supplying US troops in Afghanistan are to transport fuel for generators to power air conditioning for tents.

Obviously the climate, infrastructure, terrain, distance, domestic culture and economy are all factors.

Incidentally, this is one of the best applications for solar panels. You still want generators for backup, but you save a lot of fuel (= $, lives).

Take your entire battalion's payroll.

Multiply it by 100.

That's the quick and dirty way based on some half-remembered statistic regarding the breakdown of US taxdollars being spent on the Army.

If your mercenaries are Somalian-pirates, you need only multiply by 10. And even then, chances are clients will resist payment.

How about you simply ask the customer to take care of all the costs on his own plus pay you a fixed fee? You know, the old batteries not included deal.

EDIT:
To clarify a bit. The cost of deployment for your troops in a certain conflict will as the others have said vary greatly. None in the least because you could and should try to piggy back of the customers own supply lines. There is absolutely no reason you should not use his fuel and provisions if you can. What I am suggesting therefore is that you set a fixed premium price that you take in advance. And in addition to this you hold a running tally of any operational costs that you can the bill to the customer for later. Or not and say you did. Or not and say you piggy backed off his supply lines completely and avoid complicated calculations.

I have a gulf war breakdown of cost and daily consumption, soon as its unpacked ill post it.

What you need are compact nuclear reactors......
And a container sized hydrogenation plant that can convert anything carbonaceous you throw into it into liquid fuels. (Include dead badguys if you really want).

I remember being told that it costs a million US dollars to deploy one soldier to Iraq. Not sure if thats true, but you never know.