Free-range eggs can cost as much as 75% more to produce than battery cage eggs.

BBC: NI farms cash in on 'free-range' market

Eggs are free-range, chicken and beef British.

BBC: High street dining on trial

Dirt almost always equates to chicken manure and, if the eggs are produced in a free-range system, other raw agricultural commodities that hens might pick up from roaming freely.

FORBES: Why American Eggs Would Be Illegal In A British Supermarket, And Vice Versa