"Europe" is far too big a generalisation here. Duty-free prices vary according to country, as well as the duty-paid prices outside the country. Your route may alter this too: if you have an intra-EU flight before your intercontinental flight, there many not even be a duty-free shop at the originating airport.

Duty paid, you're looking at anything between US$8 and $90 for 200. Duty free, it tends to be between $10-$20.