Keef,
The D10A artificial horizon from Dynon which goes in your panel is around $2200 see
http://www.dynonavionics.com
Their website implies better accuracy than you quote for the sensors. Not sure how they do this but they mention three angular rate (gyro) sensors; three accelerometers and three magnetic field strength sensors. Maybe there is some clever software trickery to keep it all from drifting.
I have also seen some artificial horizons that use a PDA with a cable to the sensor box. These can then be used in the Aircraft with a piece of velcro. I am interested in how good these really are. I have met one person who had one in his Extra and he said it was very good. I was hoping to get some pruners who could provide additional user feedback