Mariah Carey Banking $1 Million for Dept. Store Gig

It's gonna be a very green Christmas for Mariah Carey ... whose services don't come cheap, but Saks Fifth Avenue is happy to ante up a sack full o' cash.

We're told Mimi's wheels up right now and Toronto-bound to help Saks debut its Christmas window displays there. MC's set to sing just 2 songs, but our Mariah sources say she's getting just shy of a million bucks from HBC -- the parent company of Saks and Hudson's Bay.

It ain't her magic number of $50 mil, but we're guessing this will do for now.

We're told one of the songs Mariah's singing is "All I Want For Christmas Is You" ... of course.

#EasyMoney

1:00 PM PT -- HBC's Director of Corporate Communications says the number we were told for Mariah's fee ... is highly inflated.