Renting
Although slightly out of date, when I did the sums accurately a few years ago; by the time you have rented, paid the pilots a descent rate, paid airport fees, FBO fees, eurocontrol fees, fuel, hotel bills, crew taxis, etc..... it was genuinely cheaper just to charter in the first place. This also had the benefit of keeping it all legal and keeping everyone happy. It also meant that there was no legal liability anywhere for the customer. Keep it neat and tidy out there guys.
MM