Should big bras cost more?

Marks & Spencer recently changed its pricing policy on big bras. We examine the reasons.

Source: The Straits Times, 9/5/9, p.C25
Headline: Marks & Spencer scraps 'big boobs' bra surcharge after revolt

Quote1
LONDON: Britain's largest clothing retailer, Marks & Spencer (M&S), has backed down on its incendiary policy of charging a two pound (S$4.45) surcharge for bras that are DD or larger. ...

Comment1
This is the decision. Let's look at the reasons.

Quote2
Some 14,000 women had lent their names to a Facebook campaign aimed at eliminating the big boob penalty. ... The group, which grew exponentially in the last few days, had vowed to challenge [CEO] Mr Rose and other M&S executives at the company's annual meeting this summer. ... "They're didn't want a lot of big-breasted women storming their meeting," said Ms [Becky] Mount, 19, [who co-founded the Busts 4 Justice Facebook group].

Comment2
This is a threat of force. We do not accept it when the robber waves his gun at the victim, and it should not be accepted here. This fallacy carries the name Argumentum ad Baculum (appeal to the stick).

Quote3
The new policy brings M&S into line with other major retailers in Britain, who decline to pass the higher cost of designing and manufacturing large-size bras on to the consumer.

Comment3
This describes the situation after the M&S decision, and was not offered as a reason. Had it been offered as a reason, the argument would have been:

Reason: Other stores charge the same price for all bras.
Conclusion: Hence, M&S should charge the same price for all bras.

This is an appeal to popular sentiment -- which could be wrong (think slavery in the 18th century). Consider if no shop could offer a discount unless every shop offers a discount. This argument carries the name Argumentum ad Populum (appeal to the gallery), and must be rejected.

Quote4
[Buyer] Ms [Nicky] Clayton said M&S probably ran into trouble because its lingerie price policy differed from the strategy used for other items. ... AP.

Comment4
Here's the argument:

Reason: M&S practises one-price-all-sizes for all other items.
Conclusion: Hence, M&S should practise one-price-all-sizes for its bras.

This is an appeal to consistency -- always a powerful call in logic. Indeed, it fits one definition of justice: that similar things should be treated similarly, and different things should be treated differently. In this case, the similar things are items of clothing, and the similar treatment is one-price-all-sizes.