Prada shoes at 70 percent off! Frette sheets for $150 a set, not $450! Four days at a Puerto Rican beach resort for the price of two! If you’re among the thousands of shoppers who subscribe to flash-sale alerts, a scan of your email inbox may read like a shopping list for the world’s largest discount store or the rallying calls of some virtual auctioneer.

“At one point, I had to put a limit on how many of these flash sales I’d subscribe to,” says D.C. media buyer and confessed flash-sale addict Meredith Kaufman, 28. “When I first started shopping on them, I probably got five or six alerts a day, and it was just too much.”

Still, if you like to buy online and you, like most people with a pulse, enjoy bargains, these short-term markets (they last from a few hours to a few days) offer a virtual warehouse of stuff and services.

Simply sign up for alerts (you can’t see what the websites are hawking without coughing up an email), then start scrolling through quirky foodstuffs, vintage housewares and Brooklyn-esque T-shirts (, haute fashions (, or kids’ toys and clothing ( You’ll be joining a cadre of other browsaholics: U.S. flash sites raked in $2 billion in 2012, according to IBISWorld market research estimates.

So are flash sales an e-commerce miracle that will save consumers money and expose them to cool brands or merchandise? Or are they an overwhelming inbox clogger and time-waster that will land you in Shopaholics Anonymous?

Not surprisingly, they’re a little bit of both.

A quick browse through one afternoon’s worth of offers (most sales go live at noon) suggests that the prices, indeed, are pretty good. On, men’s Original Penguin shorts run $30 a pair — they’re from last season, but this spring’s go for twice that. At housewares-mad Onekingslane .com, a curvy yellow wall mirror runs $299; a near-identical one at spendy is $475.

Sites also do double-duty as curators of nifty stuff, cueing fans in on goods they may not have found on their own. “Some of the things flash sales find truly are surprising,” says Jody Rohlena, deputy editor of bargain-hunting magazine ShopSmart.

This might mean blankets made of recycled Indian saris (, latkes by mail ( or vintage dresses picked out by a Brooklyn hipster (Fab .com). The prices on these sorts of things aren’t necessarily marked down in a big way, but the pieces are more interesting than what’s on the shelves at Target.

As with any form of commerce, there are pitfalls. “Don’t be romanced by the prices at a flash sale,” says D.C. stylist Lauren Rothman of “You might think, ‘OMG, a Parker maxi dress, and it’s cheap!’ But if you don’t have anywhere to wear it or shoes to go with it, it’s not a bargain.”

There’s certainly a rush to buying merchandise in a limited-time window. That, plus the sites’ tendency to post palpitation-causing cues such as “ONLY ONE LEFT!” or “IN ANOTHER MEMBER’S CART!” can goad you to nab, say, a Versailles-style birdbath when you live in a balcony-less studio.

“Yes, there’s an incentive to purchase right away at flash sales so it can feel competitive, like an eBay auction,” says Laura Swanstrom Reece, 40, who lives in Great Falls and frequently trawls flash sales.

Says Rohlena: “Those emails come relentlessly, so it can be tempting to overbuy. There’s a chance you’ll snap something up for the thrill of it.”

Still, if you keep a few tips in mind, these sales can turn up designer bargains or unusual pieces. For clothing, consider sticking to brands (and sizes) you’re familiar with. Some purchases are final, so keep this — and shipping costs — in mind when clicking and dealing.

“Shop with a list,” Rothman says. “That way, if you’re looking for summer wedges or white denim capris, you can jump on a flash-sale deal.”

For housewares and food, Google around to be sure you’re getting a better price (shipping and tax included) on that leopard-print carpet than you would at a local store or another website.

But when the timing’s right, flash sales can amount to, well, retail magic. Reece recently scored a Carolina Herrera ball gown for 75 percent off. “It makes me feel like Cinderella, and I get compliments from complete strangers,” she says.

That’s a lot of flash for not too much cash.