Convert String ($1,234.50) to Number field

[tquinn-16436437]

I have a string field that contains a dollar figure of total cost. It is a string field but I need it to be numeric so that I can use aggregate functions. I am having trouble converting the field from string to numeric. So far I am able to format the field to remove the “$” and the “,” but I have not been successful in ending up with a straight numeric field. I have included the errors I received in big query. 

Attempt 1: 

cast(replace(replace(total_costs,"$",""),",","") as INT)

error: Bad int64 value: 39500.00

Attempt 2:

cast(replace(replace(total_costs,"$",""),",","") as decimal)

error: Invalid NUMERIC value:

Can anyone please help?