That's $5 well spent.
Those '78 Grand Tourings were about the best deal in the Motobecane line up. DB Vitus tube frame mixte. High performance mixtes are sort of a rare breed. 78 was a good year. Braze ons made a return that year. My first good bike was a 78 Super Mirage. My neighbor had a Grand Touring. It was better.
Should also be pointed out that tall mixte frames were always relatively rare.