Areader who happens to be an executive at a local commercial radio station wants to know: "Why does it cost so much to run public radio stations when 80 or 90 percent of their airtime is devoted to National Public Radio programming that the local station just plugs into?"

Our reader knows how cheap radio can and should be. Once the transmitter is in place, the electricity, equipment and other basics you need to go on the air cost so little that some stations operate on well under $100,000 a year.

But just as commercial stations spend far more than that on salaries, advertising, consultants and other such paraphernalia of contemporary corporate existence, so too has public radio blossomed into big business.

In the hinterlands, plenty of community stations still get by with lots of volunteers who create programs, man phone banks and fix tape machines. But the federal government's Corporation for Public Broadcasting has pushed stations to professionalize -- that is, to hire salaried employees to do the work that volunteers did in a less formal, more creative era. The goal, especially in big cities, is a more professional sound, but the result was also very big budgets.

WAMU (88.5 FM) got in a heap of trouble as its spending ballooned, reaching a whopping $9.86 million in 2002. Just up the road in Baltimore, WYPR managed to air an almost-identical menu of National Public Radio news and talk shows, along with some locally produced talk and jazz, while spending just $2.1 million.

The Washington station took in a stunning $3.88 million in donations last year (down from $4.2 million the previous year). Another $2.15 million was generated from corporate and business sponsorships. And the station won more than $800,000 in grants, mainly from the feds.

On the other side of the ledger, nearly $6 million of the station's spending went toward programming, but WAMU also spent a jaw-dropping $2.8 million on fundraising and development and $1.1 million on management, putting the station in the red to the tune of $2.3 million.

The largest cost most public stations face is their dues to NPR, paying for the network's extensive news-gathering operation. WAMU's dues were $623,000 last year -- considerably more than the $425,000 the Baltimore station paid, because Washington is a larger market. But it's the management, fundraising consultants and other salaries that account for the bulk of the difference in spending.

Over at WETA, Washington's other public station, it's harder to pick out the finances because the TV and radio stations' numbers are folded together in a $50 million operation. But the spending on salaries is liberal -- very much on a par with commercial broadcasting. WETA's top 10 officers and employees make a total of $1.7 million a year, according to WETA's latest tax returns.

It's a far cry from public radio's roots, or its popular image as a frugal, struggling endeavor.