From 1998, the position of the Washington State Chapter of the National Organization for Women (NOW) on gender pricing. The paper notes that in some cases businesses charge women more than men, but that the bulk of pricing discrimination goes against women.
From the Capitol News Service in 1998. Similar to many of the other links I posted, this article notes that discrimination in pricing is illegal in Maryland. It further states that many businesses still get away with it by never posting their prices so that people are not aware of the price differential.
Christopher Langdon sues several bars in Florida for promotions in which he was denied free drinks that were offered to women. From the article: Lawyers for Mark NeJame, who owned the Zuma Beach Club in Florida, argue that since men pay the same price for drinks on Ladies Night as they do any other night of the week, there is no price discrimination -- rather there is a special break for women, in return for which men get the benefit of additional women at the bar (and lets face it, the reason drinks are given free or cheap to women is largely to draw in more men as well).
An article on the Unruh Act, a California statute that the California Supreme Court ruled on in 1985. In Koire v. Metro Car Wash ( 40 Cal.3d 24, 36), the California Supreme Court held that a car wash could not offer discounts to female customers on Ladies Day, and a bar could not offer free admission to females on Ladies Night.
Article on a lawsuit against Wal-Mart which had offered a Ladies Day promotion for oil changes. Plaintiff had sued on a class-action basis, but was denied the class-action status. Appeals court upheld the denial, based partially on the fact that the man's claims might not be representative of a class due to the fact that Wal-Mart gave the discount to anyone who asked for it. The plaintiff had not asked for the women only promotion.
This is the most interesting one so far. An appellate court held that the Sonics (officially known as First Northwest Industries in 1979) Ladies Night promotion violated the state Equal Rights Amendment. The plaintiff had lost a summary judgment motion. Maclean appealed that denial, and the appeals court held that as a matter of law, Maclean should win. There were no disputed facts. The case was a class action case, although I cannot find what the resulting penalties were against the Sonics. One key piece of the case was that the Sonics were operating under a lease from the City of Seattle, which brought the specter of government action into the case. I don't know if the case would have succeeded without this element. The court did hold that the Sonics violated the state ERA, but there might not have been a private right of action against a private entity. I am hosting the file to which the link points, as I could not provide a direct link to the original document. I found it by searching at Municipal Research & Services Center a service of the University of Washington, by searching for the term Maclean.