Those bikes changed pretty much every few years it seems. In the late 70s they had Vitus 172 main triangle, weighting about 25 lbs, Suntour VGT RD, and were sitting right in the middle of the Moto hierarchy below Grand Jubilee and above Super Mirage (but they had DT shifters and did not have turkey wings). Then in the mid 80s were pretty entry model with straight gauge tubes weighing about 28 lbs. But still no turkey wings or stem shifters. Need more information about your bike, like: Is there a tube material sticker of the ST? Steel rims? Components? 27 inch tires? I'd say at least $100 assuming steel wheels and entry level.