Chris Brown -- Tupac Lambo Bombs on eBay

Chris Brown's paint job on his old 2004 Lamborghini Gallardo really did a number on the resale price, because the fancy whip -- once worth $500k -- is barely notching six digits at auction on eBay.

The hot rod's starting bid ... only $89,999 -- or best offer -- and that's with a meager 16,457 miles. The Lambo has a 10 cylinder engine, goes 0-60 in under 4 seconds and comes with custom suede interior.

Breezy had a tattoo artist paint Tupac's "Lord Knows" lyrics on the car's hood and roof. If you're a Biggie or Kanye fan, this one's not for you.

So far not a single taker. There's still several hours left to bid and several people watching ... so, it could be yours.