Designer sunglasses: how much should I spend?

Well, Fiona, I'll just work this out on my special fashion calculator – it's the same one, incidentally, Elle Woods in Legally Blonde used to ace her paper, The History of Polka Dots. So, we take the uniqueness of the item, multiply it by the amount of work that went into making it, divide it by the naffness of the item itself, divide it again by the naffness of the people who wear it, subtract how easy it is to buy a version that is just as good on the high street, multiply it by how long the product lasts and, well, let's have a li'l look-see ... So that comes to ... minus £5,000,000. Spend any more than that and you're being royally ripped off.

Look, I'm as sympathetic to overspending as you'd expect someone who once bought a stupid Chloé Paddington bag. (The lining bunches up, it doesn't close properly, you can't fit anything in it, the giant lock makes it weigh a tonne – is temporary insanity a justifiable case for a tax rebate?) But when it comes to designer shades, I throw my Paddington to the ground and cry: "No! No! And thrice no – this just will not do! Paging Karl Marx: the 21st century requires your assistance!"

Of course, there is no harsher judge than a former convict and I freely hold my hands up here to admitting that, in my early 20s when I was dewy with naivete, I owned a pair of massive black Chanel sunglasses in the belief they would make me look like Jackie Kennedy (NEWSFLASH: they didn't). The gut-crunching panic I felt when I – finally and inevitably – lost them awakened me as harshly as the little boy bellowing about the king's nudity, and my nakedness was obvious to no one more than me (and to my now unprotected, sun-dazzled eyes).

Designer sunglasses are the butt-end of the worst side of the fashion world. They play entirely on the idea that fashion is merely about flaunting designer labels, quality of products be damned, and boil the idea that brand names are there to be flaunted down to its barest bones or, in this case, cheap plastic base. Whether it's those once-ubiquitous Chloé sunglasses with the diamante hearts, those now ubiquitous Tom Ford figure-8 style glasses or, yes, giant black Chanel glasses, the appeal of designer sunglasses lies simply in telling people that you have happily paid over £100 for a bit of plastic tat that you will probably sit on or lose before the week is out. You may as well walk around wearing a sign proclaiming, "I AM A TOTAL IDIOT", which would be both cheaper and more self-aware.

It is no secret that the fashion world is pretty much funded on, not the clothes (please!) and certainly not the couture (um, hello?), but the cheap stuff that is covered in designer labels so that people feel like they are getting a shimmer of the designer brand, albeit perhaps without the designer quality. Perfume, makeup, designer jeans and logo-heavy T-shirts are some of the obvious examples of this rather less than savoury foundation of the fashion business. Designer sunglasses are obviously another part, too and, like all the jeans-and-T-shirt tat that has been supporting various fashion empires more than they'd like to admit for some time, they are just worthless landfill, trash knocked out by sniggering designers who cackle as they imagine the silly rich customers who buy this stuff to prove their allegiance to the brand and the foolish poor(er) customers who think buying a pair of Armani sunglasses makes them look cool. It doesn't. This is nothing against designer brands but buying tat purely because it has designer labels on it is the opposite of cool. It is sad. It is sheep-like. And it reflects badly on everyone all round.

Seriously, Fiona, just go to the high street. H&M has brilliant sunglasses and for less than a fiver, while Topshop is always good for novelty ones that you don't mind losing after a weekend at Bestival. If you really are desperate for a designer label, not buying three pairs of designer sunglasses will buy you, depending on the label, a nice bag or skirt, and you won't, presumably, lose either of those under the seat of your car. After all, as that noted fashion commentator Loudon Wainwright III once sagely observed: "Yeah, it might feel like fun when you're sporting sunglasses, but really you're just one more fool."