For further details see page 166.
The currency had of course been depreciated before; the weight of the aureus or solidus (called by Procopius the 'stater') had dropped in the first three centuries of our era from 1/40 lb. to 1/72 lb., worth respectively £3 15s 6d and £2 2s 0d at present values. Perhaps Procopius is not looking back so far.