In message , at 13:09:23 on Mon, 3 Oct 2016,
tim... remarked:
IME (not necessarily with Amazon) postage is charged in fixed chunks
with say 6.95 as the smallest chunk,

That's simply not the case. eBay in particular encourages traders to
ship with zero postage charges. Lots of stuff "fulfilled by Amazon"
has a zero postage charge for the slowest service.

Not the stuff I bought

can't explain why, (I am not a frequent customer)

it's just how it was

YMMV, as it apparently always does.
--
Roland Perry