Minor update: Thank you so much to a very generous forum member who read the tale of how USPS took a bunch of shipping money from me, and sent me $20 and some very kind words. As I was charging extra for the last three blue PCBs to recoup my losses, I'm applying that $20 towards said losses, so now I don't have to charge as much!
Now, instead of $17.08 extra per blue board, I'm only charging $10.41 extra.
And then I will have recouped my losses from this whole sordid affair. Thank you again to the kind forum user who sent the $20.