Does Washington want to take the risk of building a ballpark that will cost $530 million to $600 million, and may have overruns beyond that, just so it can bring major league baseball back to the nation's capital after 33 years? Just as important, does the District want to take a gamble that an iconic new stadium, with the Capitol framed in its centerfield cityscape, will catalyze MCI-like development all along the Southeast waterfront?

These are serious questions without easy answers but with powerful long-term implications for the city. Washington has a once-in-a-lifetime chance. But it is not an opportunity that should be grabbed at any cost. These are questions for skeptical adults, not hyperventilating fans. And the city's decision will never be foolproof, or even particularly comfortable, no matter what the park's estimated price or the structure that stadium funding ultimately takes.

For the last 12 years, ever since Camden Yards was opened in Baltimore, expensive ballparks have been built all over America. The evidence is in. No matter how well you plan, no matter how good your civic intentions, it's risky business.

Boosters can site spectacular successes in Denver, San Diego, San Francisco and Cleveland, where new parks helped bring entire sections of cities to a level of energy and financial health that hadn't been imagined. Critics can point to Seattle, where urban development still hasn't arrived after five years, or Turner Field in Atlanta, where the town never stretched out to meet the ballpark. Was the since renamed new Comiskey Park in Chicago worth the trouble? And don't mention that ugly thing in Detroit.

As for cost overruns, they are virtually a given, usually ranging from $50 million to $100 million over original budget.

For the last two months, the ranting has been fun. Everybody who wanted to vent has had a chance, pro or con. Amid the fuss, most skeletons, especially worst-case scenarios on costs, have been shaken out of the closet. Now we know that Mayor Anthony A. Williams's original estimate of $440 million was far too low. Credible estimates from $530 million to $580 million have surfaced as the real ballpark range. Post reporters have come up with a plausible estimate as high as $614 million. The story didn't include the possibility of a meteor striking the construction site, but it didn't miss much else that might go wrong.

Now, it's time for the political posturing and punditry to take a back seat. What's needed is a sense of proportion. And that's just what's been missing -- a sense of the relative proportion of the risks and rewards in this project.

The worst-case and the best-case ballpark scenarios -- especially for a town that doesn't even have a team -- are not on the same order of magnitude. The potential for disappointment and wasted money is significant. But, as other towns have shown, the pain passes. The possible benefits of a successful team in a beautiful park that generates significant economic value, from new jobs to a larger tax base, are huge in scale both in economic and intangible terms. And they can keep giving for generations.

On one hand is manageable failure. On the other, there is enormous success that can last for many decades. The old Senators, bad as they were, made Washington a richer place for 70 years.

Can Washington afford to risk building a park that (gasp) comes in at $650 million? Can we risk that the team might leave town someday? It could happen eventually, even though this area is three to four times the size of the city that lost the Senators twice. Those are fair questions. With no shortage of people asking them.

On the other hand, can Washington afford not to risk bringing the Expos here? The rebuilding of Pennsylvania Avenue was not a five-year project. It took 25 years to see all the benefits of the original vision. The impact of MCI Center is undeniable. In a city with so many blighted areas, can the District afford not to take a shot at the benefits that may flow to both sides of the Anacostia River? What is the nightmare of overruns, which may never happen, compared to that lasting dream?

Great changes don't happen by magic. They often require risks. You have to spend money to make money. But it still takes courage to do it. San Diego's waterfront ballpark has been finished less than two years and the development around it already constitutes almost a quarter of the entire downtown.

In the last two months of debate, the failure to define terms has done enormous damage to clear discussion. Before the last act arrives, Washington needs to get one thing straight: The money for this park is not coming out of some huge pot of public money that also goes to schools, hospitals and libraries.

It's simply not true. As soon as a politician or commentator tells you that the park will be built with money that should be going to better causes, hold up your hand and say: "Wait. That's just wrong. You either don't understand or you're lying."

The current park proposal gets money from three sources. The team's owners pay rent. That's sure not public money. There will be a tax of 10 to 13 percent on every ticket, soda and parking space. Without a new ballpark, none of those taxes would exist. That money is not coming out of any pot. Finally, the rest of the funds will come from the largest D.C. businesses. These are new taxes: a new pot, not the old pot. The D.C. business community (they spend money to make money) is on board with this plan, although nervously since overruns will hit them (not libraries). Baseball, at least in the District, is not a zero sum financial game. About 2 million fans a season who live in our suburbs would patronize a new park. They would be hit with those taxes on everything they spend. They would also be dropping dollars at new Southeast restaurants and clubs. That's called increasing a city's tax base. And it's good for everybody.

One argument against the economics of new ballparks is that you're just redistributing money within one tax jurisdiction. So nothing is gained. It's a good point. But the geography of this area is unique. About 80 percent of fans will bring cash from the suburbs into the city. Without baseball, that money never arrives. That blows up the whole idea of 'no net economic benefit.'

At the moment, the District sits at the intersection of short-term civic cost and long-term social benefit. There is some ballpark price that is too high to pay, some financial risk too great to take. The D.C. Council must decide where is that cut-off point.

However, when an entire section of a major city is revitalized and that new energy and prosperity keeps giving for decades, how many zeroes does it take to measure the total value to the town? What have the Cubs been worth to Chicago? Red Sox fans just celebrated their first World Series title in 86 years. And here's the kicker: Boston enjoyed the wait.

Seen in that long-term perspective, does anybody in Boston remember whether Fenway Park came in on budget?