[Arran]

12AT7 / 4024 Mullard NOS is about $40 apiece.

Mike;
  Buy the Phillips or Valvo labeled 12AT7s, same tubes but a cheaper price. In spite of what the audiophools think Mullard tubes are just Phillips tubes made in a British plant with a different label. I would not be surprised if these NOS tubes that tested weak were actually used tubes that some serviceman put into the box after he replaced the tube in the amp or TV set.
Regards
Arran