FYI to all, I've never been able to figure out prices (using USPS website) for Priority Mail, except the flat rate. I've used the Regional box A many times. It's usually cheaper than the small flat rate box if the box doesn't need to cross a mountain range. I've shipped many things from MN to MI ...as well as TX...it's like $6 or $7.
I had a bag of brass go today to Texas. The padded flat rate envelope was $10.40 I asked the clerk how much it would be for Priority cubical (that is what they call the rate schedule if I use the now discontinued Regional A box. The shipping for that came to $25 (from MN to TX). So I guess I won't be using my stash of Regional A boxes.