Ok corerect me if I'm wrong (and IO'm sure people will), but the only people who should demand that shopkeepers sell at a specific price is the city leader, in conjunxction with their minister of trade.
It is not up to the Guildmasters to declare city policy on trading.
The Guilds can charge anything they like, but when the shops get hold of it, priovided it is not a Guild shop, then it becomes the pconcern of the city, not the Guild.
The Guilds are perfectly enttiled to take legal action against such shops, but it is still the city's domain, and not the Guilds.

Guiliaume

(BTW, I'm opn Tenlet. Excuse the bad typing.)

Penned by my hand on the 1st of Valnuary, in the year 267 AF.