I have been a bit of a lurker in here and thought it was high time that I posted something. I have picked up quite a few as this is my bread and butter price range. All of these were bought for between £45 and £140. Some needed servicing on top of this price but even with that all still less than half the price cut off.
This blue Gen 1 Dynamic for $400 was my Omega purchase under $500 this year. The dial wasn't perfect but it was in very good condition for an Ebay find. Didn't stay under $500 for long as the movement was loose in the case requiring a trip to the watchmaker. And the "original band" was all but disintegrated.
The Cimier slide rule watch was my first automatic watch I owned back when I was about 10 in the early 1970s. I couldn't even remember the brand but found a picture of it based on the slide rule bezel. Not a true chronograph, the pushers only start and stop the second hand. Got it for sentimental reasons for about $130.