Maybe "Hiljada" is only South Slavic, and is borrowed from "Kilo" greek word.
But again there are differencies between Thousand, Kilo, and Mile !
That means that were several invasions which created aryan languages.
We may group Balto-slavic and Indo-iranian, in one language groups, which show the affects of R1a1 invasion. For example "Jedan" (serbian), yeden (polish), Yek (Roma).
In the west languages, is present the letter N, for example, one (english), Eins (german), Uno (latin), Një (albanian), Enya (greek), etc.
We conclude that, one expansion created the word YE*, and another expansion created word ENE* (with "E" I mean just a sound, and not "e").
So, some words are comon for all IE, but some other words are comon only for a group of IE.