After some extensive and expensive trail and campground work in Colorado's Sangre de Cristo mountains, the U.S. Forest Service has floated the idea of charging for access to the four 14,000-foot peaks -- Crestone, Crestone Needle, Kit Carson, and Humboldt -- generally reached from the South Colony lakes in Custer County.

The proposed fees are not substantial ($10 for the trail and $20 for camping), and they're supposed to serve two purposes: Recovering some of the costs of restoring an overused area, and deterring some potential climbers, so that the area won't get so much use.

"Less use" sounds like economic trouble for mountain towns that rely on nearby Fourteeners as tourist attractions, though. Fourteeners attract at least 100,000 people a year, and perhaps as many as 500,000, to Colorado's highest country. They're the basis of an industry that goes beyond guides, pack animals and motel rooms to guidebooks, maps, picture books, pins, decals, calendars, postcards and other material limited only by American commercial imagination. Fourteener spending is relatively recession-proof; it barely budged after the 2007 economic downturn.

"It's certainly a major part of our business," said Keith Baker, owner of the Trailhead, an outdoor shop in Buena Vista, Colo. (whose slogan until recently was "Home of the Fourteeners," although now it's merely "8,000 feet above average.") Buena Vista promotes summer whitewater sports in the Arkansas River, but "I hate to think how bad our summer business would be without our Fourteeners," Baker said. The town sits in the middle of Chaffee County, which boasts a dozen such summits. "Last year we sold more Fourteener maps and guides, in dollar volume, than we did men's clothing."

On the other side of the Mosquito Range, the old mining camp of Alma has 275 residents. Near town are three Fourteeners: Lincoln, Democrat, and Bross. The trails cross off-and-on mining operations that extend well above timberline. Worried about liability if a hiker should wander into a collapsing tunnel or tumble down an old shaft, the property owners wanted the routes closed, and the U.S. Forest service complied in 2005.

The closures noticeably damaged Alma's economy, so the town government leased surface easements over the mining claims. This covered the routes under the town's insurance and removed liability from the property owners, who then re-opened the trails. "We were prepared to spend some money on this," town administrator Nancy Comer said; like me, she had read somewhere that the Fourteeners accounted for 10 jobs in and around Alma. She laughed. "They're important to our economy, no doubt, but I couldn't put my finger on those jobs."

So what part of the Fourteener economy can you put your finger on?

Some answers come from Catherine M. Keske, who holds a Ph.D. in agricultural and resource economics and teaches at Colorado State University in Fort Collins. Thanks to two research projects based on questionnaires at trailheads, she may well be the world's leading authority on the economics of Fourteeners, although she concedes "that has to be a very small field."

Greatly simplified, here are some of her findings. The average amount spent on climbing a Fourteener in 2005 was $337.58 per group, per trip. That breaks down to $178.78 per group per day, and $107.18 per person per day (the average "group" size is 1.7 climbers). The largest expense categories are restaurants, gasoline, and motel rooms -- the kind of spending that pleases small-town chambers of commerce.

As for access fees, Keske's survey didn't ask about them directly, since so many people oppose fees in principle and that would skew the survey. Instead, respondents were asked if they'd still make the trip if it cost $XXX more. The additional $2 to $950 (the amount varied on surveys so as to compare different values) could be the result of $10-a-gallon gasoline or $500 motel rooms, for all the respondents knew.  A user fee of $70 per climber, comparable to the price of a ski lift ticket, would reduce Fourteener traffic by about 20 percent, Keske found.

As to how much more they're willing to pay, climbers come in two groups -- those willing to substitute another hike if their planned outing cost too much, and those who'd pay the tab for the peak they had in mind. The substituters would pay, on average, up to an $88 fee before they'd move to another hike, whereas the non-substituters would pay, on average, $294 for their preferred Fourteener.

Would people actually pay fees? They already do pay $100 to climb Culebra Peak, the Colorado Fourteener that sits on private property, so we know the answer. By and large, they could afford it, since "Fourteener visitors are predominantly male, high education and high income" with a median annual income of $85,000.

Fees might even improve the economies of little mountain towns. Westcliffe is the seat of Custer County, the home of popular routes to four Fourteeners. Jim Little, publisher of the weekly Wet Mountain Tribune there,  said, "It would make the peaks even more special to people, and they'd be more likely to make it more of a two- or three-day trip, rather than just drive up for the day. So we might have fewer tourists, but they'd be spending more."

Fewer tourists spending more -- that sounds like a pretty good deal, no matter how much one might hate access fees in principle.