The market delivered five straight days of gains last week as easing of fears in Europe helped investors brush aside concerns about the economy on the home front.

Don’t count your winnings too quickly.

On Monday, stocks sold off significantly. A late-day rally cut the losses in the session by more than half. Once again, worries about default in Europe swayed investor sentiment. When will the madness end? I’m half-tempted to say buy your stocks then disappear for a few years. When you return, all of these issues will have sorted out and you should be solidly ahead of the game.

Unfortunately, telling an investor to disappear sounds all too much like the failed “buy and hold” mentality we have seen disappoint all too often during the last decade or more. And professional investors are flummoxed by the current environment. So what strategy should investors follow?

My suggestion would be to find business models that work — not in the future, but today. There can be little patience for pie-in-the-sky speculation. You need businesses that will make money now and tomorrow no matter what happens in the economy.

The fight for the consumer dollar in a down economy is quite simple: Have the lowest price in the market, and you likely will win the fight. It really is that simple. From an investing standpoint, here are three companies winning the low-price battle to consider for your portfolio:

Teva Pharmaceutical

Anyone listening to the battle in Washington has heard about the high cost of health care, including drugs. It would be a pretty safe assumption that a drug company selling medicine at the lowest price would do well in this economy. In the pharmaceutical space, that means focusing on companies selling generic drugs. My pick would be Teva Pharmaceutical (NASDAQ:TEVA)

It is far too expensive and risky to buy a research-and-development drug company. If you haven’t noticed, drug pipelines have been shrinking. While there is great excitement and potential in the space, there has been a dearth of blockbuster drugs coming to market.

At the same time, older drugs are losing patent protection. Those expirations build the pipeline of a company like Teva. The best part is Teva doesn’t have to invest in expensive research and development to sell new product.

Investors in Teva don’t share the same enthusiasm, but that is what creates opportunity today. The stock is down 28% so far this year. Wall Street expects the company to make $5.05 per share in the current year. In the following year, profits are anticipated to jump 13% to $5.72 per share. At current prices, Teva trades for only 7.5 times current-year estimated earnings.

That is relatively cheap for this low-cost drug seller. In addition to that low valuation, the company pays a nice dividend. I would buy the stock at these levels.

Southwest Airlines

The airline sector is a great study in conflicting information. On one hand, planes are full. On the other hand, an industry group is anticipating a significant drop in demand during the rest of the year. Who do we believe?

Stocks in the sector have been absolutely crushed this year. High oil prices are taking a toll on profits even with planes filled to capacity.

The industry assessment of the future prospects includes a note about demand for economy travel. The number of passengers in that category exceeds pre-recession levels. That’s a good thing for discount airlines like Southwest Airlines (NYSE:LUV).

Shares of the popular point-to-point air carrier are down 33% in 2011. Those losses accelerated after the company reported results for the quarter ending June 30 that missed Wall Street estimates by five cents per share.

For the full year, Southwest is expected to make 33 cents per share. In 2012, profits are slated to increase by more than 100% to 75 cents per share. That impressive growth should attract any type of investor. With the stock trading for just 26 times current-year estimated earnings, the company can afford a misstep or two.

Even if demand declines, the economy space should do well as consumers gravitate to the lowest-cost provider. In the air category, that would be Southwest. I would buy the stock of this low-price king.

Travelzoo

One thing investors should avoid in this market is hype. Paying a huge premium to own a stock believed to have monster potential rarely works out well for the investor. This year’s buzz is all about social networking, with one of the most anticipated initial public offerings coming with Groupon.

That fairly ubiquitous company has made a name for itself by providing consumers discounts on everything from haircuts to a glass of wine. It is a good model but not likely to live up to the hype. Instead, I would look at a stock like Travelzoo (NASDAQ:TZOO).

That company started offering discounts in the travel space. Now, Travelzoo uses its database muscle to offer the same sort of discounts being sold by Groupon. Instead of trading for a nosebleed valuation likely to be attached to Groupon when it comes public, Travelzoo has been bloodied and tested.

The company is profitable and its shares trade for a reasonable valuation, with the stock down some 70% this year. Wall Street expects Travelzoo to make $1.41 per share in the current year. Next year, those profits are expected to jump nearly 30% to $1.82 per share. At current prices, the company trades for just 23 times current-year estimates of earnings.

I suspect Groupon will be much more expensive when it finally comes to market. I would buy Travelzoo as demand for discounts is likely to be strong for some time.