I still remember when my lecture said about SAP consultant one year ago. If you are end user and you are deploying SAP, becarefull with your brightest SAP programmer/analyst asset. SAP will try to get your programmer/analyst work with them, and your company become depend on SAP. SAP will charge with consultancy rate 10 times than normal salary of your SAP programmer/analyst, and the consultant sometime are your previous programmer/analyst :-) What a strategy!
This practice actually not only happen in SAP, but also in Telco environment. I just notice last week when somebody say exactly the same scheme happen in huge Telco vendor, guess who ? Pay attention with your brightest enginner/programmer and create a system that you have backup engineer/programmer with similar quality. Some telco have agreement with the vendor where vendor can't hire person from the telco.
The services from vendor take important role for vendor's revenue. With selling services, vendor will still get annual revenue from end users. Without it, vendor only can get revenue every 3-4 years.