Everyone knows there are two dollars to the pound, and that everything in America is twice the size and half the price. We’re also well aware that goods from iPods to designer jeans are being handed out like UN food parcels to any British tourist on Fifth Avenue. But that’s not the half of it.

For the real deal – and I’m talking about bargains so outrageous, you’ll recoup the cost of your air fare in a New York minute – you need to meet the Elegant Tightwad.

The Noo Yoik fashion diva Pamela Parisi and her delightful sidekick, Pilar, aka the Tightwad, specialise in taking ladies of impeccable taste – and their reluctant husbands, if necessary – on exclusive undercover tours of Manhattan’s secret fashion outlets.

It all happens in the posh part of town, where New York City’s consignment stores lie nestled on the leafy streets of the Upper East Side. Such shops aren’t that common in the UK, so I’ll explain the concept.

Uptown girls, spoilt heiresses and the bored wives of Wall Street billionaires buy ludicrously expensive clothing, wear it once, or not at all, then take it to the consignment store. The deal is that the store sells it for whatever it can get, and the consignor receives 50%.

“Clothes often come in with the tags still on,” says Jonathan Tse, owner of La Boutique (1045 Madison Avenue; www.laboutiqueresale.com), “like this Prada suit.” The original price tag – $1,450 (£735) – is still attached. Jonathan wants just £125. Does he see celebrities in here? Oh, yes. Is he naming names? Of course not.

An hour of animated rummaging by my awestruck wife resulted in a haul comprising a Moschino suit, an Etro top, Manolo Blahnik shoes, a Marimekko skirt, an Escada alligator wallet and a pair of vintage Yves Saint Laurent earrings. Retail price: £3,330. La Boutique price: £485. And there’s more.

At Margoth (218 East 81st Street; 00 1-212 988 7688), an increasingly excited Mrs H found a Chanel suit for £220, a Marc Jacobs top for £35, a Valentino dress for £175 and Jimmy Choo sandals for £65. “We get new stuff in every day,” explained the eponymous proprietor. “And I mean new.” She holds up a Chanel handbag, tags still attached. “This is this season’s line. It’s $2,000 (£1,012) at Saks. We want $1,250 (£633).” Waging a bargain-basement blitzkrieg, we moved on to Tamara’s Pret-A-Reporter (235 East 81st Street; 212 717 2691), which I had been hoping was a sandwich bar for exhausted journalists. It turned out to be another little shop of delights, crowded with high-maintenance blondes and ladies who never lunched, chatting on mobiles while unabashedly slipping into little Vera Wang gowns and Stella McCartney numbers, and still getting change from £100. But the best was yet to come.

“Those in the know come here first,” says Myrna Skoller, who set up Designer Resale (324 East 81st Street; www.designerclothingconsignment.com) 17 years ago. “Then they go on to Saks. They call us the Miracle on 81st Street.”

Myrna’s biggest sale to date was a £12,600 Hermès alligator Kelly bag, which went for £5,000. It was part of a haul of 1,500 items consigned to the shop by the wife of a Palm Beach tycoon who went bankrupt to the tune of $270m.

The store has three branches, including a rather disappointing menswear section, and, as my now hyperventilating spouse scurried to and fro with armfuls of frocks, I had a rummage through the racks. Here’s what I found: an Oscar de la Renta silk couture gown, Oscar’s price £2,025, Myrna’s price £63; a Nina Ricci purple silk gown, down from £1,012 to £101; an Armani ivory silk dress, reduced from £1,012 to £63; a pair of Rock & Republic jeans for £13; a John Galliano dress, original cost God knows what, yours for £150; and Versace bags, Prada handbags, Tiffany jewellery, Gucci shoes, all 10 a penny.

There were eight more stores on the Elegant Tightwads’ list, but I was getting tired and emotional by this stage, so we diverted to the bar at the Carlyle – which is exactly the kind of shop I like.

— The Elegant Tightwad (00 1 631 841 2111, www.theeleganttightwad.com) has three-hour Consignment Crawls for £30

Travel details:Silverjet (0844 855 0111, www.flysilverjet.com) flies business class to New York; from £999 return. British Airways (0870 850 9850, www.ba.com) and Virgin (0870 574 7747, www.virgin-atlantic.com) have returns from £240. For luxury Upper East Side accommodation, try the Carlyle (00 800 8767 3966, www.thecarlyle.com; doubles from £275) or the Jumeirah Essex House (00 1 212 247 0300, www.jumeirahessexhouse.com; doubles from £172), overlooking Central Park. HotelPronto (0870 405 9455, www.hotelpronto.com) has live pricing deals on dozens of New York hotels.

Remember, only the first £145 worth of overseas purchases are tax- and duty-free; after that, you’re liable to Vat at 17.5% and duty at 12%. HM Revenue & Customs says: “If in doubt, go through the red channel.” But it would.

What about the boys?

LET’S MAKE one thing clear: other than the immeasurable pleasure of trotting behind your sweetheart like a love-struck lamb, there is absolutely nothing of interest on an Upper East Side shopping trip for a gentleman.

So play nicely and claim a little payback when she’s emptied out the shops. Need jeans, but don’t want to waste time like a lady? Call the denim expert Lance Smith (00 1 212 753 4000 ext 1744), at Saks Fifth Avenue (611 Fifth Avenue), and tell him you’re in a hurry. He can also post jeans to your home address.

Paragon Sports (867 Broadway) stocks every outdoor brand from Adidas to Zeiss. A classic North Face Nuptse down jacket costs £99 here, compared with £150 at home, and Converse sneakers are just £15 – cheaper than a secondhand pair on eBay at home.

But enough about the clothes – what about the kit? Visit the Apple store (767 Fifth Avenue) for a £75 iPod. A new camera? Avoid the rip-off joints around Times Square and head to Adorama (42 West 18th Street), where a Leica D-Lux 3 10mp compact, which retails at about £500 in the UK, costs £299.

Or how about a drink instead?