When adding a text object to a label that will display a Cost from an external data source (csv, Excel, etc) the currency symbol will not be displayed as part of the text object. To correct this, you will need to use the Format Value setting from the Content tab for the text object.

Depending on how you want the amount to appear, there are two different ways to enter this. Click on Format Value, then in the Format String box, enter $0 for whole dollars, £0 for whole pounds, etc. For dollars and cents, enter $0.00. For pounds and pence, enter  £0.00.