Koroibete has never played a professional game in the 15-man code in Australia but was named in Cheika's 32-man squad for the season-ending tour after coming off his fifth season in Australia's top-flight National Rugby League.
His inclusion came at the expense of two-test Queensland back Luke Morahan and sparked criticism from local pundits and rugby fans that the Wallabies jersey was being given up cheaply.
"The fact of the matter is I am not cheapening the jersey because he hasn't got one yet," Cheika told reporters on a conference call on Wednesday.
"No-one's getting a jersey for free, no-one has and no-one will.
"I think he's obviously a talent who can contribute for us and make an impact further down the road, definitely."
The 24-year-old Koroibete will start playing Super Rugby for Melbourne Rebels next year after two seasons with NRL club Melbourne Storm.
The explosive flyer is not expected to debut in the November-December tests against Wales, Scotland, Ireland, France and England.
But Cheika said he could see him taking the field in the mid-week match against a French Barbarians team late in November and would not rule him out of a test debut if injuries piled up.
"It'll give me an opportunity to coach him a little bit first before he goes back to play Super Rugby, and I think that's a perfectly logical thing to do," Cheika said.
"He's grown up playing rugby, (it's not) like he doesn't know the game. I'm not going to be giving him another jersey just for the sake of it.
"It's the smart thing for us to do."
Will Genia has been named in the squad but Cheika was unable to confirm whether his first-choice scrumhalf would be available for the tour opener against Wales in Cardiff on November 5.
