I am currently building an invoice application. I have had no issues getting a user to create an invoice including line items and their price.
If the user goes to edit the invoice (created separate screens for ‘edit’ that are different from the ‘create’ screens), there are default values in the form fields. That allows the user to see the values they already put in when they created the invoice and can choose to edit or not. So far so good.
However, there is an issue with numbers in the thousands after a user saves the form. Numbers in the thousands seem to be divided by a thousand (or my guess is that the comma in the thousands is considered as a decimal). That results in a number going from 1,200 to 1.2 after the user saves the edit form.