It really depends on the country of origin, but assuming a British farthing in average circulated condition, a few cents to at most a dollar or so unless you can identify it as a rare variety.
A fathing from the 1940s would not hold much value today. In good condition, they may be worth a few cents to a couple of dollars to a collector. However, their numismatic value is generally low.
an instrument
The value would depend greatly on its condition.
$2.00
$1,000,000
guitar violin piano and fathing farteress
the safety bicycle. >;|
$1200 to $1600.
3-5 cents
Much about the same it is now: Catholicism.
£500.00
In the 1940s Pizza had become very popular. You could buy a slice for about 25 cents at the pizzeria.
Similar to today, but with much less merchandise.