I wonder if this will work inside the table?
Create a helper column inside the structured table with this formula:
=IFERROR(VALUE([@[Expense Amount]]), 0)

or

Use array-aware formulas and LET for Clarity. I had to look this one up.

=LET(expenses, OfficeForms.Table[Expense Amount], numericExpenses, IFERROR(VALUE(expenses), 0), numericExpenses)

outside the table this may do the trick, but I'm sure you want it inside the table.

=IFERROR(VALUE(INDEX(OfficeForms.Table[Expense Amount], ROW()-ROW($A$2)+1)), 0)

Adjust $A$2 based on where the table starts.