The message
from "Franz Heymann" contains these words:

I found a supplier of a compost based on bracken and horse manure. The
price is almost exactly twice as much as that of ordinary peat based potting
compost. Is this a rip-off?

Isn't the composted bracken/manure product is intended as a
fertiliser/soil enricher? Potting compost is intended for what it says.
If they are not equivalent products then one wouldn't expect the prices
to be similar.

Compare it with the price of other composted manures like 6X , which
is also twice the price of ordinary potting compost.

Janet.