Here in Paris, it really depends. Bettas at chain stores outside of the city proper are about 6 euros each, but woefully uncared-for. The bettas in the city's chain stores are about 10 - 15 euros each, and mostly crowntails. I've never seen females for sale in the chain stores.
At the LFS where I got my Modi, they are all halfmoons and a whopping 30 to 50 euros each (sorority females for around 15 euros), but in great condition, spoiled to the limit with live foods and 20-gallon community tanks, and sourced from local breeders instead of Southeast Asia.