The costs of doing such things include...

1. Half-done projects started by some happy staff who then went on to start the next project in the next shiny new thing and either more-or-less completed by someone who was just about capable of cut-n-pasting without understanding or who decided that some new shiny thing needed to be added to make the rest wonderful.

2. A monstrous stack of projects in 637 different programming languages, frameworks, ideologies, coding styles, and indentation levels, guaranteed to require rewriting for any change. Result: 638 different things.