Between the spreading European crisis and the continued financial-market see-saw, it's been a tough spring for luxury retailers, or any merchant that sells to the 1%.

Some luxury names have gotten smacked down, including Tiffany (NYSE: TIF), which sank to a 52-week low after its second disappointing quarterly report in a row. But that doesn't mean investors should stay away from luxury stocks, in fact, it's putting stocks like Tiffany on the "buying opportunity" list.

Yes, luxury sales look to be cooling a bit, after being a bright spot in retail for most of the past two years. Some observers are seeing warning signs among the well-heeled that mid-priced retail will have to pick up some slack. According to the monthly tally from the International Council of Shopping Centers, luxury department-store sales growth is slower so far this year -- 7% through May, compared with 7.9% this time in 2011.

When Citibank's Deborah Weinswig recently took Macy's (NYSE: M) off Citi's Top Picks list, she noted one of the reasons was that there are signs that affluent consumers are pulling back. That adds a risk of a sales slowdown at Bloomingdale's, which she estimated makes up 10% of Macy's sales.

In the company's latest analyst conference call, Polo Ralph Lauren (NYSE: RL) COO Roger Farah warned that "geopolitical issues are likely to dominate the consumer psyche for some time" in Europe. Tiffany also acknowledged that Europe weighed down its results for the current quarter, along with the uncertainty in the stock market that kept domestic sales down.

But if you dig down, the fears that the rich the world over will stop shopping are unfounded. Farah said international revenue is now 36% of the company's total, up from 20% five years ago. More good news: Sales are even growing in Europe, where the growth rate rose from the teens to 26% in the latest quarter.

Time to take the money and run, before Europe's crisis gums up the works? Not really; a few monthly sales dips may spook some investors and drive down these stocks, but in the long term, the iconic brands will recover. Those are the first ones the consumers will turn to when they have discretionary power.

The Chinese have a ravenous appetite for luxury goods, and Japan is now past the anniversary of the tsunami, which means easier year-over-year comparisons. Any slack in European sales should be picked up by growth in Asia. Tiffany has been taking it on the chin because it depends heavily on sales at its Fifth Avenue flagship, and that's gotten hit by a slowdown in sales.

But that little blue box has power, as does Lauren's Polo pony and Coach's (NYSE: COH) logo. When the brand consultant Interbrand ranked the most valuable retail brands in the U.S., the only luxury names in the top 50 were Coach (No. 7) and Tiffany (No. 20).

Even now, some names seem almost bulletproof. As she was talking down Bloomingdale's, Weinswig stayed high on Saks (NYSE: SKS), noting it was the only retailer to beat Citi's expectations when announcing monthly sales for May. Coach also looks impervious to harm. It reported an excellent first quarter, with earnings up 24%.  Lauren posted a blowout quarter, too, as Seth Jayson pointed out, but it gets only a two-star CAPS rating among Fools.  

Ralph Lauren is trading at a P/E around 20 -- hardly inflated, and still way off the consensus target price of $174. Coach, too, is far from its $84.50 target price and has an even lower P/E around 18. Tiffany is even lower at around 16, and its consensus price of $68.50 is quite a bit away.

Unless we see a replay of the French Revolution and they build a guillotine in Central Park, Wall Street isn't going anywhere. The market will recover and the masters of the universe will go on spending on luxury goods.

And we will see growth again in the lower end, too. Yes, all these brands are aspirational, and the people who aspire to them can't afford them right now. But when this recession-or-whatever-it-is ends, they will shop again. And they will want the brands that they know mean luxury: Tiffany, Polo, Coach. Buy them now and hang on.

If you're not sure about the outlook for luxury and just want to watch and wait, try adding these stocks to your free My Watchlist and keep an eye on them.