Seriously, look second hand. The bike I just built for the missus consists of:
Ebay:
2004 Stumpy FSR frame (baby blue, very important, took ages to find)
In garage:
2007 Revelation U-Turn, set to 100mm
2005 Mavic 717s on XT hubs
From Soul:
2008 Race Face Deus XC drivetrain
2008 Elixir CRs
2006 XTR shifters and mechs
From classifieds:
Easton Stem
Easton Bars
Bought new:
ODI grips
Wellgo V8 copy pedals
Most/all of what came out of the garage and off the Soul initially came from the classifieds on here so it’s hard to tell, but I’d be surprised if it cost me much more than £800 to build.
I could have got a newer frame for the same or less money but 100mm is about right for what she’ll use it for, and the colour was important (natch). There was a cracking 2007 S-Works stumpy (120mm) frame on here not so long ago for less than £200 IIRC.