Workflow Calculated Currency Value Not Saving

Hi,

I am having issues with saving a read only calculated currency value to our database from a workflow screen.

I have a custom JS function that is updating all of the values on screen.

The screenshot below shows the section of the workflow action screen when it loads

Extra 1 is a selection field. I am using a switch to assign a numeric value to the string selected in extra1

After a change is made in Extra1 or Quantity the code runs to update Extra 1 Cost. However, the currency symbol is now missing and when I save no value is entered on our Lead DB for this field.

To update the specific field I am using the lines below

var extra1cost = (parseFloat(extra1val) * parseFloat(ex1q).toFixed(2));

$('#_Datalead_extra1cost').text(extra1cost);
$('#_HIDDENlead_extra1cost').val(extra1cost);

Any help here would be greatly appreciated.

Cian