Britney -- Shopped 'Til She Dropped $3,000!

Further proof Britney Spears was completely sane during her frantic shopping spree Tuesday afternoon: She spent nearly $3,000 in 15 minutes!!!!

We're told some of the items Brit Brit bought at the Vionnet Boutique in Beverly Hills were...

-- $175 silk lace camisole
-- $345 tourmaline ring
-- $520 total on two lace trim slip dresses
-- $200 aqua & lavender ring
-- $195 tank with lace

One of the outfits (left) she even wore right out of the store.

Unfortunately, one of her purchases was not a new weave.