Labor is a part of ERP implementation. a company will spend a lot of money on labor for the implementation but it is unlikely you will guess right. Every ERP  system contains a lot of data. You can be sure that data contained in one table must be converted into multiple tables and vice-versa.  Some costs can be controlled by limiting the amount of historical data moved. Some Businesses hire consultants from their ERP provider who gives him advice and guidance.  And they will also bill you hundreds of dollar per hour.

People will need to learn new skills. A new ERP allows users to build reports and dashboards within the system. Some example of skills that need to be trained. You should be sure to invest in cross-functional training, an ERP is an enterprise-wide set of tools. Once completing a  functional training user need additional training for ERP.

Customization means you choose to modify the ERP you selected to fit some need that ERP does not address. The developers of that ERP tried to incorporate best practices from around the globe. Integration is another practice related to customization. ERP meets all your business needs except that it does not offer a web storefront.

ERP providers typically charge maintenance fees that cover support calls and which your users will need. Support costs also include bug fixes and continued improvements to the basic system.

Test using the new ERP system with data converted from your legacy system. You will find there was some default set up that caused some errors. You also find the converted data did not fit into the system as expected. So you need to fix the problem and test it again.