Form calculation not populating field

"Monthly Total" should populate after selecting a "Step 1: Base Membership", and it is not...

As per checking, it seems that the issue is with the dollar sign ($) on your formula. The dollar sign ($) is being treated as a number (black box) but it should be treated as a string (brown box).

Just click on the dollar sign ($) to change it from a number (black box) to a string (brown box).

Once you have changed this, the Monthly Total should be populated.

Do let us know if you need further assistance.