"Foyles' quixotic system of trading"
Paying was only half of it. The other half was the way books were displayed. The common habit of grouping books by subject wasn't for Foyles. They shelved their books by publisher.
If, by chance, all the good books on CodeMangle-- were published by, say Wiley, this was fine. If every publisher had a book out on it you'd wander all over the shop trying to compare them. And if nobody had one out you'd wander all over the shop simply to discover that.
At one time the bus-stop outside bore an advert reading "Foyled again? Try Dillons."