Each is not obligatory.
There are three robots on the shelf in a toy shop.
Customer: How much are the robots?
Shop assistant: They are one hundred dollars./They are one hundred dollars each.
Are they both natural in the dialogue of the Shop assistant? Is 'each' obligatory?
Thanks.
Each is not obligatory.
I guess without eachone hundred dollars can be understood as the price for all three robots on the shelf in the toy shop.
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