Though iPhone had 6 milion sells in their first week and samsung is having around 5, these are global products. Motorola is selling only in the us market and that is why they are happy with their 100k result.
A news also came that, like apple, motorola is also planning a cost reduced moto x version. This will be a miniature version of the original moto x. It will have the same design as the moto x original. Motorola is hoping that, they will be able to grab a huge market with their new one.