Ah, you're using an Edit form, in View mode. For that case (which uses a text input control) there's no way to directly set the format of the data that is going to be displayed.
One thing you can do is to have two controls, the text input that comes with the card, and add another label on top of it. Depending on the mode of the form, you can toggle the Visible property of the controls, like in the set of properties below:
DataCardValueX.Visible: EditForm1.Mode <> FormMode.View
NewLabelInCard.Visible: EditForm1.Mode = FormMode.View
NewLabelInCard.X: DataCardValueX.X
NewLabelInCard.Y: DataCardValueX.Y
NewLabelInCard.Height: DataCardValueX.Height
NewLabelInCard.Width: DataCardValueX.Width
NewLabelInCard.Text: Text(Parent.Default, "[$-en-US]$0.00")