Depends what materials you're using. Probably about... 20k, not including materials... I'm no good with this sort of thing, all I know about it is from reading my mum's developer magazine xD
Stables- Not sure about 6 but i've been quoted £20,000 for 26 internal stables from IAE! Monarch are more expensive and IMO their product is not as good as IAE.
And do you want a barn? If so i've been quoted £40,000 for a 108 foot x 64 foot steel framed building.