From sheldon brown's website on vintage lightweights:
In the late 60's Frejus and Legnano bikes were very popular. They had a "Cinelliesque" seatstay attachment, fun paint with great contrasting panels, and lots of Italian character. Actually, Frejus bikes from the 50's are somewhat common in this country. The famous shop in New York run by the recently deceased Thomas Avenia was the focal point for both Frejus and Legnano bikes in this country.
Most Frejus bikes feature rather mediocre workmanship, but there are moments of precision. It doesn't matter. These were the bikes that scores or U.S racers rode during the dark days of U.S bicycle racing when a small but highly dedicated group of enthusiasts upheld the cycling faith. Besides, a clean or restored Frejus IS a beautiful bike. These bikes are collectible for all these reasons and more.
The value of an older Frejus will depend on its specific parts. An early 60's model with "raised pedal lip cranks", an original leather saddle, and other goodies, could be worth close to $ 2000. Earlier bikes with more interesting but not as rare parts perhaps $1000 - $1200. Bikes from the 60's with Record equipment are probably worth around $ 1400. Late 60's models with oilers in both the headtube and botom bracket are worth about $1300. Early 70's models with perhaps one oiler and full N.R. are worth perhaps $ 1,200.
In the early 70's, Frejus became more intertwined with Legnano (one bought the other) and certain changes were made. A head decal replaced the headbadge, an eventually the classic seat cluster. was discontinued. As the bikes become more generic, there value falls. The most bland models should be worth about $ 750.