Kobe Bryant -- My Bald Head Costs $830 to Groom

Kobe Bryant somehow managed to rack up a $833.75 grooming bill on a recent Nike shoot ... which is pretty steep considering the guy has no hair and reportedly refuses to wear makeup on set.

TMZ Sports has obtained a copy of the invoice ... which shows Nike coughed up $750 for grooming services for the Mamba -- PLUS, the Swoosh sprung for a 15% tip.

We spoke with a rep for Nike ... who tells us "Kobe doesn't typically wear makeup during the shoots, so the grooming would be primarily for hair."

Interesting, considering Kobe essentially rocks the bald look.

For the record, Supercuts will shave your head for $18.