Also, with Mainframe, you’re not only using a different machine but also a different “everything”. You need specialized storage, you need to use an “exotic” programming language, you need people who know JCL, RACF, DB2 etc., for a lot of “middleware” (CD pipeline, access management, version control) you have limited vendors to choose from so you’ll pay a lot for that too. So if you are also running something else (Linux servers etc.) you basically need double the staff and licensing costs...