Numbeo takes its numbers from people who report them, so I suppose it also varies where people shop when it comes to groceries, but still…
Recent example of cost-reporting on their homepage. A small cappuccino costs €1.50 in Verona, Italy. It costs 49.50 NOK in Stavanger. Converted to a mutual denominator, such as dollars, a cappuccino costs just under $2 (or $1.9 to be precise) in Verona, whereas in Stavanger it costs a bit over $8 (or $8.2 to be precise).
However, to weigh up for the high cost of living, the salaries are also fairly compatible. Mostly. Which again drives up the cost… and the cycle continues.