Design or Redesign?

I’m looking for statistics that analyze how much more time it takes to re-design a poorly constructed database (including data conversion) vs starting all over from scratch. (primarily MS Access, but I don’t think the file type necessarily matters)

Have any of you ever seen any such comparison? We have a division that wants to do their own thing, but then they want IS to fix it after they’ve made a total mess of things. We’d rather they let us design it from the get-go.

Thanks for yourhelp,
Lynnette