Columbus SLX bikes/framesets come to market on a regular basis in varying degrees of condition from beat to death to mint New Old Stock (NOS) and from high end well know manufactuers to lesser known makes. Overall condition, amount of chroming and the manufactuer all come into pricing consideration.
I'll be very blunt and honest when I tell you a Miele is nothing special. Your is in average condition.
Prices of ramesets vary from $125 to $600. My best guesstimate for yours is $200-250.