I have noticed that the 600 series goes for high prices on ebay lately .
Funny, because it's just about the most entry level vintage Omega you can find (with the possible exception of some Geneve models), especially in a gold-plated case.
But maybe the vintage watch market is starting to rebound a little overall.
I agree that it is an entry level Omega , but it has a good classic look , and i think it looks better then some non entry level Omega's .
I think that the 600 series is a bit sought after by small \ starter watch collectors , which explains the prices .
10 -12 years back I bought them in excellent condition for 100-200 usd