How to copy a cell formula in Numbers
Using the built-in method

As per Apple’s Knowledge Base, Numbers supports absolute references:


  You can set row and column references in a formula to be absolute so that you can use the same formula elsewhere in your spreadsheet without the cell references changing, as they would otherwise.


To change your original formula to use absolute references, follow these steps:


Double-click on the original cell to go into edit mode.
For each reference, click on the triangle; then tick both boxes Preserve Row and Preserve Column.


Or, as an alternative to step 2, you can manually edit the reference to say e. g. $A$1 instead of A1.

The obvious drawbacks of this method are:


The method basically locks your formula in a mode that makes it hard to reuse the same formula in other places where you actually want flexible references.
If you you want to copy many different original formulas, you need to repeat the method over and over.