Based on the serial number, the frame was manufactured in early 1985 by Rizzato,owners of the Atala brand since 1938 and Italy's largest bicycle company at the time. It is not a contract manufactured frame. Rizzato also owned Lygie during this era, which would explain similarities between the two brands. It is a well respected brand but since it was a full range brand, it does not have the same prestige as the small volume boutique brands, at least in North America. I'd place it in the same category as a high end Bianchi or Bottecchia.
The model is a Professionisti (Professional). It was available in both SL and SLX versions. SLX became commercially available for the 1984 model year, so it is a possibility. However, the SLX decal is the later 1988+ version, so the decal is a replacement and the tubeset may not be SLX. The SL fork decal is appropriate for 1984-1987 SLX. To verify SLX, the OP would have to remove the bottom bracket and examine the the inside ends of the seat tube, down tube and chain stays for the helical ridges indicative of SLX.
Regarding price, IMO this a $1000+ bicycle despite some component mismatch.