It is hard for startups to replace the real value of SAP, because it is a standard ERP basis+auxiliary apps, all integrated on the same data. You will spend years to build e.g. the payroll system, and then you only have one piece of the puzzle. Thus it has become the standard for large companies (e.g. many companies in BRIC countries are now adopting it). And it is very powerful and stable software, for which you are guaranteed to find experts to fix problems that might put your company's production at risk.