Musician/Standard Bearer? On the same strip, then you can potentially reuse them if you make other infantry types? Hint, hint

.
Cost per unit? Hmmm.
Commercially you can pick up a newly cast infantry unit for £5-£6 or so. Plus P+P. But the big boys have got volume sales, you haven't (yet?

). I tend to make reasonable sized purchases - £20-£40, so the postage becomes insignificant. I do feel a little uncomfortable if I'm only spending a few pounds and getting charged the same amount for postage as I would for a larger purchase though - but maybe that's just me.
You've got to source padded envelopes (50p each?) and the postage is variable. Plus a little for your time and effort actually going to the post office obviously. £2 minimum P+P?
You're making something no one else does, so people should be prepared to pay a slight premium, without feeling ripped off. I'd guess most people would only buy a small number of these units, so postage might be a factor for some people.
Somewhere in the region of £8-£10/unit including postage to the UK? Maybe £12 worldwide? If you could quote the postage for 1, 2, 3, 4, etc. units, people may take the plunge and buy more units up front. If you can do it for less than that, great - I'm a Yorkshireman, what else would you expect?
Could you take, say, up to 4 units to the Post Office and ask them how much it would be to post different numbers to the UK/Europe/Worldwide, then you can give more tailored prices and maybe generate more sales. "I'm being charged £10 for a single unit but 4 units works out at £9 each, ah to heck with it, I'll buy 4", for example. Obviously visit the post office at a quiet time!
Maybe get "a lot" (whatever that means) cast up and sell them on e-bay? A far bigger audience than this website.
If all that waffle makes sense?!