How much do you think this Eddy Merckx bike is worth?

This looks like a very nice bike, except for the rust. If purchased, it should really be stripped and cleaned, then repainted. The rusting is typical of a bike that has been used on a trainer, sweat would drip precisely where the rusting is happening. If you could get it for no more tan $350, and had it repainted, this would be a lovely bike to ride, as long as it is a good fit for you. Although the components are dated, they are good quality with one proviso. This vintage Dura Ace is incompatible with other Shimano components. The cette body will only accept a Dura Ace cette, the shifters will only work with the Dura Ace derailleur, so if things wear out(and they always do) you may have to search a bit, and pay more for replacement parts.