Edit: Someone on Facebook pointed out there would be no items priced at exactly £1, which had occurred to me too. It got me thinking about an interesting quirk of English on display here.
If you were to say “Some of the fish are blue” then that implies nothing about the colours of any other fish. Similarly for “Some of the fish are yellow”. But just conjoin the sentences into “Some of the fish are blue and some of the fish are yellow” and suddenly it’s heavily implied that there are no red fish present. Not explicitly stated, but I would almost certainly read it that way and I guess others would too.