1999 - 2000 price for a new, equipped Beech 58 was US$1,000,000.
Bet they don't sell too many.........
Dunno about your claim you can operate a C550 at lower seat/mile cost than a B200. You checked out JT15D engine overhaul costs lately?
As an exec aircraft, it's probably a matter of choise - and the C550 is much nicer - but if you need to worry about the cost you shouldn't be buying one.
But in general charter (excluding specialised operations) you probably need at least 16 plus bums aft in a turbine twin to be cost effective. As GAF discovered some years ago!
Woomera