It is a 'free market'. They can charge what they like.100% and this goes for agriculture too. There is no coordinated food policy and we are producing less and less annually as we lose land to everything from housing and solar farms to rewilding and flood management projects.
Above all, we need policy that enables farmers to make a fair living from producing the food we all need. Otherwise the current crisis in British farming will take us past the point of being able to recover - just like steel and other industries.
Ukraine and now the current global trade crisis continue to underline the folly of relying on imports of the foods that we can produce in the Uk.
Albeit supermarkets may then find it cheaper to import from Holland and elsewhere.
Maybe we could put tariffs on foreign farm produce?

Edit: or maybe absolve them of paying fair taxes?
I suppose it all depends on whether UK farming can be regarded as strategically important.
Anyway, there are loads of Big farms and they don't seem bothered about the need for subsidies....
(Apologies for being provocative; we have discussed all this before, but its you who has brought it up again.
Personally, despite being a lefty, I am not in favour of subsidies to deal with unfair foreign competition.
If a product is cheap because it has been subsidized by the (Chinese) government or made by child/slave labour,
we should ban it.....)