My post office here in Brick, NJ says #000 bubble mailers are automatically $1.13 for the first ounce and .17 cents for each additional ounce.

If I go to a nearby post office branch in a local drug store, she charges me .80 cents postage for the same bubble mailer with one chip. However, when that package gets to its final destination ... there is nothing to prevent that far end post office from affixing Postage Due notices o the recipient.