What we have here appears to be a terminology issue. My local post office ... and many others ... classify bubble mailers as "Large Envelopes" (not letters) at .80 cents minimum and because of the additional thickness adds on a surcharge. A bubble mailer up to one-ounce in Brick, NJ will cost $1.13 to mail. Nowhere does the chart below use the word "bulk". I'm also told that the term "letters" means not being rigid ... as with carboard fillers and or SAF-T mailers.

I know that there are several USPS employees who are chippers and who read this message board regularly. Perhaps they can give us the straight "skinny".