To calculate a character's total worth, each equipment is 30% of the original price, and ship itself 50% of the original price.
So, you purchase a Barge for 500 millions, which means worth of the ship itself is 250 millions. Also, Cap8 being 895 millions if bought from a base, the worth would be 268.5 millions.
This makes total worth of a Cap8 Barge with no cash on it (Although rest of the equipment worth is so small it doesn't really count anyways) would be ~520 millions.
Maximum worth of each char without getting corrupted is 2.1 bils, but people say it's safer if you don't go over 1.8 bils at all... So, you can have about 1290 mils on a Cap8 Barge and still be safe.
Edit:
Before you ask me where I'm gettin this info from:
' Wrote:The actual limit is based on the total value of credits, cargo, equipment + ship. This must be less than 2147483648.