Theres way more to MSG-3 than bridging at a convenient interval (it ain't B check) and then going flying at lower maintenance costs and higher reliability, especially with any Classic MSG-2 aircraft. MSG-3 is a good option for a high utilization operator and was originally contemplated for such, not VIP ops. In addition to program approval and solid bridging, operators require reliabilty programs that do more than report on last months failures and ops departments that can write up defects on something other than the last sector of the day while turning final into the main base.
A successful B727 operator in British Columbia has accomplished this with good reliabilty numbers and reduced costs but it wasn't easy or cheap.