In old money
Definition 1 of 2
Pro Tip 1/3Historical Currency
Used when converting current money to a currency that was used in the past, often to emphasize change. 
This vintage wine would have cost £10 in old money.
Pro Tip 2/3Nostalgia Trigger
Invokes a sense of nostalgia or historical interest, especially among those familiar with the 'old' currency. 
My grandfather often talks about how things were only a shilling in old money.
Pro Tip 3/3Comparative Value
Helps understand the value of things before inflation or monetary changes took place. 
In old money, a loaf of bread was a few pence, believe it or not.