in 1970 3p then in 1972 when decimalised 5 new pence!
then that depends on the size of a standard sized single bar is about 89 cents depending on where you live and if food it taxed.
in a 62.5 gram mars bar there are 11 teaspoons of sugar.
Usually between a nickel and a dime.
Depends on which one. usually around $2.50