What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
I'm afraid not, this is not available on a Matrix field.
You can only automatically add a dollar sign in front of numbers being typed into the Masked Input widget:
Or you can add a dollar sign to numbers calculated inside a Form Calculation widget:
Furthermore, when you use a Number type of field inside the Matrix, it cannot contain any other characters except for numbers. The dollar sign cannot be placed in a Number type of field, neither by being typed it by your users, nor by your form having it as a predefined value in front of numbers.