CBS radio has paid $2.5 million in a two-year contract for a 36-game National Football League package, including Monday night games, sources said yesterday.

The Mutual Network paid from $400,000 package that was not attractive as the new programming, which includes 10 postseason games, including the Super-Bowl.

Mutual has broadcast Sunday and Monday night games for the last half-dozen seasons.

ABC, which telecasts Monday night games, indicated initially interest in bidding on the new package along with Mutual, NBC and CBS, but ABC dis nor make a bid.

A source said the CBS cannot break even, even if that network sells the games for the top commercial minute price on radio - $5,000, which commentator Paul Harvey used to command on ABC radio.

It was predicted that CBS may lose $1.5 million over the two years of the contract. It was speculated that CBS bought the package knowing that it would be a "loss leader," a prestige device.

The three networks combined paid about $240 million to the National Football League to televise its game in the four years ending in 1977. They paid more than 2 1/2 times as much for the next four years $648 million or $5 million-plus for each club each season averaged over four years.