NEW YORK (CNN/Money) - As expected, a sharp drop in ratings this past season is costing NBC Television Group hundreds of millions of dollars in lost revenues, according to reports Monday.

Advertising Age reported Monday that NBC is signing up advertisers for the coming television season at rates that are below last year's prices. The industry trade publication, citing unnamed sources, said the General Electric unit's rates were down as much as three percent in some instances.

NBC rivals and media industry analysts have been predicting for weeks that NBC could lose upwards of $600 million in advertising during this year's "upfront," an annual ritual during which broadcast and cable networks line up advertiser commitments for the television season that begins in the fall.

MediaWeek magazine reported Monday that NBC could bring in $2 billion in advertiser commitments during this year's upfront. That's 30 percent below last year's $2.8 billion.

NBC could also have more than the usual amount of commercial slots held over for sale during the "scatter" market, a period closer to airtime when the risks are higher for networks and advertisers because rates fluctuate. Networks typically sell about 80 percent of their commercial inventory during the upfront; MediaWeek reported that NBC was looking at a 65 percent sellout.

NBC, which has long dominated primetime ratings and commanded the highest rates of any rival, saw ratings fall 17 percent during the season that began in September and ended May 25. The network was unable to recover from the last year's loss of "Friends," a hole that a series of ho-hum shows this season could not fill.

NBC finished the season fourth both among total viewers and the 18- to 49- year-old viewers whom advertisers pay top dollar to reach, according to Nielsen Media Research.

MediaWeek said NBC made a bad bet during this year's upfront by holding out for rate increases despite its ratings shortfall. MediaWeek said NBC was hoping its lead as the top network for 18- to 49- year-old viewers who make $100,000 or more would help it raise rates by 2 percent.

Apparently, it didn't. Advertisers instead flocked to Viacom's CBS, the top primetime network and a close second to Fox among viewers aged 18 to 49 years. CBS executives claim the network negotiated $2.5 billion to $2.6 billion in deals, the most of any network by far.

ABC, meanwhile, benefited from its ratings rebound with $2.1 billion worth of advertiser commitments, a 20 percent jump from last year. Fox, owned by News Corp (Research)., reported roughly $1.6 billion in upfront deals, about flat from 2004.

All three networks claimed they sold ad time during this year's upfront at rates that were 4 to 6 percent higher than last year.

Overall the broadcast television upfront is expected to be flat or slightly down compared to last year.

Jack Myers, an independent media analyst, told CNN/Money that he was not concerned over reports that NBC had lowered its ad rates given the network's ratings.

Myers called lower rates "an adjustment on NBC's part that accurately reflects where they have to be this year to (draw advertisers)."

Even still, Myers said NBC would still command the highest ad rates in the industry -- the only possible exception being CBS.