Why do goods marketed at women cost a third more than their male equivalents?

If you've still yet to read the comments on Amazon underneath the Bic For Her – all 340 of them – then you're in for a treat. Highlights include “AT LAST! Bic, the great liberator, has released a womanly pen that my gentle baby hands can use without fear of unlady-like callouses and bruises” and “Grate procduct S 5tars! but #need a k3ybrd 4 grls PLZ!” For the privilege of having a writing implement that's pastel-coloured and slightly thinner “to fit women's hands”, Bic is charging £22 for a box of 12, compared to £1.99 for a pack of 10 bog-standard ballpoints. No doubt a Bic for Her couldn't handle those kinds of sums, but something here doesn't add up.

While Bic's lady pen has become a meme in its own right, one wonders how long it will be before the Gillette Venus Embrace Razor (£12.75 compared to £7.20 for the male equivalent) and the Sure for Women Bright Bouquet Deodorant (£3.39 compared to £3.15) follow suit. An investigation by The Times, which analysed hundreds of products from toys to toothbrushes, has found that items marketed at women are 37 per cent more expensive.

It's been called the “sexist surcharge”, the “pastel tax” and the “pink premium” and now MPs have waded in, with Maria Miller, the chairwoman of the Commons women and equalities committee, announcing that she will be looking at launching an investigation into whether it constitutes discrimination. If she does, she'll be following in the footsteps of the French finance ministry, who in 2014 ordered an investigation into why female shoppers were paying more for the exact same products, with Pascale Boistard, Secretary of State for Women's Rights tweeting “Is pink a luxury colour?” Quelle horreur!

But it's not just pink sparkly razors and rose-scented shower gels. Women are paying over the odds for almost everything – from dry cleaning to haircuts. A study into gender pricing in New York, released last month, found that women pay on average seven per cent more for a variety of items and services, declaring that over the course of a woman's life the financial impact of the disparity is “significant”.

So, other than opting for men's deodorant (and putting up with smelling like “invisible ice”, or “apocalypse”, or whatever the latest Lynx is called), what else can women do to close the price gap?

Jemima Olchawski, Head of Policy and Insight at the Fawcett Society, which campaigns for women's rights, says the onus is on shops to change, not consumers. “These are high-street retailers and brands that lots of women use and they are risking losing that loyalty if they don't develop more gender-neutral lines that are priced fairly,” she says. “The idea that razors and pens need to be dressed up to appeal to women and sold at an inflated price is absurd.”

But Carol McKenzie, a researcher in retail and marketing at the University of Stirling, says the issue is more complicated than that. “I think we need a full investigation into where the price increase happens – is it the retailer, the supplier, the manufacturer, the marketing?” she asks. “Research into women's shopping habits reveals that these prices might be deliberately discriminatory, because women actually like to spend more on toiletries and grooming. They see them as a luxury or a treat, the ”because I'm worth it“ effect.”

The “ladies levy” (I just made that one up) has been an accepted phenomenon since a 1995 study resulted in California becoming the first and only US state to ban gender-discriminatory pricing. But pink and blue marketing can be traced back to the 1980s – according to Jo B Paoletti, historian and author – when it became more common for parents to find out the gender of their babies in utero, and retailers began to cater to this demand for gendered toys.

There are however, a few items where men get a bad deal. The Times study found that male children's underpants were more expensive than the female equivalent. Car insurance and male-specific skincare are also areas where the price is often skewed in women's favour. So if you're a woman who happens to enjoy wearing Aladdin Y-fronts and using Nivea for Men, you're really in trouble.