Okay, lets just get this straight. Price fixing involves a supplier mandating a price that a retailer must sell a product at. In other words Supplier A tells retailer B that product X must be sold at $500, otherwise they'll stop supplying it.
That conduct is illegal in here Australia, as a breach of the Trade Practices Act, and I'm sure it'd be illegal everywhere else.
Your presumption is incorrect, at least here in the United States.
The Sherman antitrust act, as interpreted by the U.S. Supreme Court in 1911 in the Dr. Miles Medical case, held that an AGREEMENT among the mfr and dealers to establish minimum prices led to the "destruction of competition and the fixing of prices, are injurious to the public interest and void."
However, under the Colgate doctrine (named for the 1919 U.S. Supreme Court case), a mfr may unilaterally set minimum resale prices, and if a dealer refused to comply, the mfr can simply terminate such dealers without running afoul of the law. In other words, so long as there is no AGREEMENT among the mfr and resellers on a minimum resale price scheme, there is no violation of the Sherman Act.
Many mfrs of products that are relatively unique, exclusive and non-fungible have enforced minimum resale prices under the Colgate doctrine. Most are mfrs of high-end, designer brand goods.
In the case of Apple, they have succeeded in developing products that in the eyes of many consumers are non-fungible. The iPod is an example where most consumers will not settle for an alternative mp3 player. This gives Apple power to dictate to dealers what prices they may sell the iPod at or they risk being cut off as an authorized reseller.
BTW, the Dr. Miles case was overturned this year in the Leegin case, so that even if there is an agreement between the mfr and dealer, it is not presumptively illegal; i.e., the court will consider whether it is in violation of the Sherman Act on a case-by-case basis.