> What makes it that expensive that no one wants to rewrite them in a modern language? From a business perspective there may not be much to gain from doing so.

> What makes it that expensive that no one wants to rewrite them in a modern language? From a business perspective there may not be much to gain from doing so. If the old software works in a current environment then there often isn't a justification for the cost of rewriting/testing/integrating just to end-up with the same thing in a shiny new language.