Bieber to French Montana -- Nice Workin' With You ... Here's a $150k Thank You

Justin Bieber knows how to show gratitude ... he bought French Montana a $150,000 chain after working with him on a song.

Justin presented the chain to French back in November for his birthday, but it would seem their bond in the recording studio upped the ante for the gift. Justin and French recorded the song in July, along with Mariah Carey and T.I.

Apparently the chain wasn't tricked out enough for French, because he just got it iced out with diamonds for an additional $90k.

Just a token of appreciation.