Under Pining

I have a client who wishes to remove the floor under the house and create another 2.4 m space , this will cut into the exlusion zone , there are about 50 meters of footing that need to be underpined , so has any one here had this done and what would be the going rate for this,

It involves , digging down 600mm under the footing at a length of 1 meter , then missing 1 meter, and doing it again , around the entire parim then , filling these holes with steel and concrete , grouting the joint with a non shrink grout and then digging the other remaining meters out and doing this all again, so the old footings are sitting on new ones ?? what would you expect to pay for this kind of work??