Justin Bieber's New 'Invisible' Diamond Grill Runs About $50k

If you blinked, you might've missed the fact Justin Bieber's got himself a new set of diamond whites in the form of a grill ... and it costs a fortune.

The Biebs showed off his new bling Tuesday on Instagram, but only barely. You gotta look close, but he's got the grill laid out over the lower half of his teeth -- he left his upper deck untouched, but that bottom row sure is shiny when you see it up and close.

JB was a bit modest in showing it off, but we got you covered!!!

The grill was commissioned by an L.A.-area jeweler who goes by Gold Teeth God -- with a name like that, he's gotta be pretty good, right?!? He is, 'cause Justin gave him a buzz.

We're told JB asked for the grill two weeks ago, and just got it delivered this week. It's called an "Invisible Set Princess Cut Diamond Grill" ... which means the teeth aren't individually outlined and appear flush. It ain't cheap -- it runs about $50,000.

It comes fully loaded too -- we're told the grill was designed to cover 8 teeth with white gold and white Vs1 diamonds at a clip of 7.65 carats total.

This is at least Bieber's second grill -- you'll recall ... he got an all-pink one made for him a couple years back that ran a clean $15k (top and bottom too at the time).