I guess for line edit, you will need to store the value in a variable, and show contents based on that in the view.
For that you may need to catch editingFinished() or returnPressed() signal of the lineedit, get the text 2500, store it in a variable. Convert it to $2.500 format, and use QLineEdit::setText to set the text in line edit.

Also if you are using some View(inherited from QAbstractItemView), you can use delegates to show the text in desired format.