Yeah, this is an 80s bike not 70s.

Condition doesn't look TOO bad besides the flat bar conversion. But is the left DT shifter boss missing? Missing the shifter itself isn't too terrible but if the boss is gone that will have a huge impact on value.

From what I can see in the condition pictured I wouldn't pay more than $75 or so. I would have to know if that shifter boss is there or not.

Edit: assuming the boss is there, I would still not go above $150. I don't see more than that with the condition and parts that are on it. FYI I'm fairly certain a shifter boss is something that's part of the frame, not something you can just replace. So if it's gone the frame is nearly worthless. Your only other options for a front shifter would be to use a clamp-on shifter or use handlebar mounted shifters with a clamp-on cable stop. Either way, frame damage like that will kill the value.