By law he can't charge you more than a equal share of fuel only. He can't charge you for any operating expenses beyond fuel, operating expenses will far exceed fuel. Example, if your cost for 5 employees is $200, his cost will be about $500.
A Piper Meridian with 6 adults with and bags sounds kind of heavy too.
Actually he can charge you for 1/2 of the prorated expenses of the trip. Including Fuel, Oil, Airport fees, Engine & Prop reserves, etc. RE:FAR61.113
So if it cost $500/hr dry and fuel is $150/hr; he can charge you $325/hr plus half of any handling fees that might be incurred.
But Frank brings up a great point: 6 guys and bags in Meridian??
I'd like to see that W/B sheet.