In 1950, my dad earned about $50-100 (not sure exchange rate at the time) per month and considered middle-class.
So translated; 40 cents was ~0.5% of a month's salary. Today a monthly salary is ~$3000, so 2 drinks are ~$15. Around here, that is about right, ~$9-15 each depending on place.
If that were true he wouldnt be able to buy anything eith it. The fact that the value changes over long periods of time is not the same as saying its worthless..
Money should have a store of value but does not need to be a "perfect store of value"... money can loose value over time, so long as it is a slow process, and it is still a store of value.
Much like a bucket that very slowly leaks is still a store of water, it just isnt a perfect store of water.
But more important to the fact is that this is a **desirable** quality... We want money to slowly loose value because that encourages investment rather than hoarding.