Lot of variables involved which can effect price
Location of wall, is it in a built up area or high traffic area which will involve more costs including health and safety issues and possible local authority costs including insurance if work will extend onto a public road or footpath.
Original wall foundation will almost certainly need to be replaced, also is the wall in close proximity to services.
Is the (boundary) wall part of a property registered as a protected structure, in this case a local authority may take the view that planning permission may be required or at least insist in agreeing with you the standard of works required to rebuild the wall to a satisfactory standard.
Labour rates in stone masonry will depend on the stone used and the standard of finish required.
This is a worst case scenario, best option is to get a stone mason to visit site and give you a written quote to rebuild the wall.