I very much doubt you would get 11% at FRA. Also you would have to pay Tax (unless you are airside) and claim it back afterwards.
The collection at Lufthansa is generally more expensive (e.g. Topas IATA LH: €489, Topas IATA KD: €449 - 11%) and has the LH Badge on them. Next time I'm around FRA, I will compare the retailer prices there.
Lufthansas Shop for (price) comparison is
www.worldshop.eu