>Just customizing something like PeopleSoft to fit is a large task in itself, let alone trying to implement bespoke software
Customizing large enterprise software is more like writing bespoke software than it is what most people think of when you use the word customization. You end up paying enormous vendor margins on top of the costs for something that is effectively bespoke software.
There is so much bespoke software out there that is at least as complex as government payroll software.