It seems like an irrefutable truth—improve your sales efficiency, and you’ll get more sales for less cost and you’ll squeeze more results out of the same number of hours in the day. What could possibly be wrong with that?

Believe it or not, quite a bit; that’s because efficiency savings rarely come out of nowhere. Like pushing on an inflated balloon or playing a game of Whac-A-Mole, what you save in efficiency can cost you in effectiveness. Put another way, what you think you save in sales may actually cost you in marketing.

There are two main ways this can happen: One is by looking for cheaper lead generation, and the other is by looking for sharper lead qualification.

Cutting Your Cost per Lead

You can always reduce your cost per lead; just find a medium that offers lower cost exposure. Ah, but it’s not that simple. There’s a reason Mercedes dealers don’t advertise on Craigslist, and it’s not just cost per lead—it also has to do with marketing and the messages you want to send.

Buyers of a Mercedes (or any other high-end product) view themselves as very particular people. Their sense of self is reflected in a thousand ways, ranging from the restaurants they frequent to the shoes they wear—and most certainly their buying habits.

Your average Mercedes buyer may use Craigslist—just not to buy a Mercedes. How you sell is a big part of marketing who you are. You wouldn’t wear a pair of faded jeans on a sales call to a bank; it sends the wrong marketing message. Using the wrong kind of lead generation does the same thing; it sends the wrong marketing message.

Cutting Your Sales Cost Through Better Lead Qualification

Most of us get why not to wear jeans on a corporate sales call. Not nearly as many of us get how tighter lead qualification can actually hurt marketing. After all, what could be wrong with saving time, focusing on high-quality leads and quickly eliminating wasted sales effort?

Well, remember Julia Roberts’ famous shopping scenes in the 1991 movie Pretty Woman? At first, she’s snubbed by the salesladies in the fancy Rodeo Drive stores; later, of course, she returns in triumph. Those salesladies were simply doing lead qualification, screening out a low-probability sale.

You might say “What are the odds of a customer returning in a week with millions to spend?” Well, the odds are vastly greater than they were in 1991. Not every snubbed buyer will be worth a fortune, but everyone has friends—and they all have Facebook pages and Twitter handles—and they talk. A lot.

Every time you screen someone out—especially if it’s in a way that can feel hurtful—you’re poisoning your own well, taking away your own brand equity and personal reputation.

Suppose you visit a financial planner only to be politely but clearly told you don’t have sufficient assets to qualify for their advice. What would you tell your friends about that planner? Don’t make your customers feel that way.

Suppose you go to a jeweler to buy something special for a loved one, and the jeweler makes you feel cheap for not wanting to look at something far more expensive than you can afford. Would you refer your friends to that jeweler?

The truth is, great lead qualification can actually improve your marketing as well as cut sales costs. When you screen someone out, take a few minutes to explain clearly why the fit is not right (if you can’t explain why, you have a bigger problem). Offer them some free advice on where else to look, if you can. Do something to make them feel glad they came to you, even if it didn’t work out as they planned.

It costs you but a few minutes, and the impact can be huge. That’s not bad selling; that’s great marketing.