Montgomery County has snagged a deal that puts the best Black Friday doorbusters to shame - a new radio communications system for first responders, for only $39.9 million.

Previous estimates had been in the range of $70 million to $100 million.

The county had been shopping for a system since 2010, and last month decided to negotiate with Motorola Solutions instead of going through the competitive bidding process.

"Those negotiations came to a frenzy" Wednesday," said Commissioner Bruce L. Castor Jr., and the vote was rushed onto the board's agenda Thursday morning. The commissioners voted unanimously - and ecstatically - in favor.

Castor, who led a panel of local police and fire officials to assess the county's radio needs, said it might be "the most significant decision the commissioners have faced in the five years that I've been commissioner, and maybe in the 28 years I've served in county government."

So how did the price get so low? The county's consultant said Motorola could offer a lower price if didn't have to bid, and noted that the company already has towers and equipment in the county.

But the price tag came down even further after the consultant's recommendation in November, compelling the commissioners to decide on the contract in their last meeting of 2012.

Motorola's negotiator did not respond to requests for comment. (Motorola Solutions is a separate company from Motorola Home, which has a plant in Horsham and was sold Wednesday to a Georgia-based firm.)

Under the three-part contract, the county will pay $23.9 million for 10 new towers and other infrastructure improvements needed to upgrade 3,400 existing radio units.

An additional $6.1 million will buy 1,800 new radio units. The commissioners have yet to decide where those funds will come from, and indicated that they may pass some or all of the bill to local police and fire agencies that use the system.

Finally, a $9.9 million service and maintenance program will come out of the county's general-fund budget.

The new system will use microwave relays to provide broader and clearer coverage.

Dead zones have been a consistent problem since the current 800 MHz system was installed in the 1990s, leaving law enforcement personnel unable to communicate around corners in the same building or when crossing into neighboring jurisdictions.

Chairman Josh Shapiro said the commission would decide early in 2013 "how, when and where" to borrow the money to pay for the project. The county this year has battled multimillion-dollar budget deficits and a depleted reserve fund that prompted Moody's Investors Service to downgrade its bond rating.

Contact Jessica Parks at 610-313-8117, @JS-Parks or jparks@philly.com.