Amazon.com is NOT an european website definitively. It's an american online shop.
Those examples are NOT valid, because they are in USD not in Euros, so let me show you how both models retail in Europe.
First example: Here in dv247.com, that is a british online shop:
As you can see, the Audio-Technica ATH-M50s is 3 pounds more expensive than the Shure SRH840.
Other example: In Amazon.de, that is a german online shop:
The Shure SRH840 is slightly more expensive, less than 10€, than the Audio-Technica ATH-M50.
Third example: In Amazon.co.uk, another british online shop:
Again the Audio-Technica ATH-M50 is more expensive than the Shure SRH840.
I think that is enough with three examples, but I can post some more is someone is still sceptic about the similarities in the price. So with these 3 examples you can see that the prices for Europe for the Audio-Technica ATH-M50 are considerably higher than in the USA and because of that, the Audio-Technica ATH-M50 and the Shure SRH840 cost more or less the same.