Do you run cam software now? The learning curve is quite a bit of work. If your people use pro engineer than putting it all in a package is how proe works best. PTC has changed the way you can find the cost of modules so someone else will have to tell you that. There are a bunch of us tied to proe that run proman. If you want top down manufacturing pro nc is the only way to go. If you don't care about that there are a lot of better and more user friendly cam softwares out there to use. If I was not working with a group running pro e I would not buy the software. There was a guy asking about using proe and proman to make molds and dies yesterday and I bet he will be 30,000 to 40'000 grand unless the snake oil sales people give him a"deal" then he will pay that in maintenance.
The Complete Machining module is about $12K if I remember correctly. We have 1 seat of Complete, 2 seats of Expert Machinist and 2 seats of Advanced machining. It is the only CAM software that we use. While the learning curve is very steep, it is well worth the effort in that your GCode is completely associated with the model and you have the ability to manage the program through the part's entire lifecycle - which is virtually impossible with 3rd party software, where you are always re-importing IGES files, etc.
The simple rule is that if you are designing the part in Pro/E, then you really should machine the part with Pro/NC.