Maybe the deal is that some of the coins posted can't be had for $300 but worse examples can be had for under $300. When it isn't in your collection yet you don't have a picture to post, so you search one out and generally find and post a nice one.
As for my vote, I got it like this.
1. Alexander Tetradrachm. No problems under $300 but maybe not the nicest one. About the size of a quarter but about a half ounce of silver. Great coin. Only other coin I could put above it for $300 would be the Athens Owls, but those usually have a big test cut in them at the sub $300 price.
2. Alexander Drachm. I'd double dip on Alexander no problem. About the size of a dime. Can do a decent one for $100 or less depending on what draws your eye. Probably get a great one for $300, not that I have looked in that price range.
3. Ionia Miletos Silver Diobol or 1/12th Stater. Not picture yet. Pictured below.

Like all coins, these depend on the condition, but are fairly common for what may be the world's oldest silver coin (6th - 5th century BC; the city was destroyed in 494 BC).
Small coin at 1.1 grams or so and 10mm.
I like it for its age and it is another denomination / type. The story of Miletus is pretty good too.
4. I haven't seen one yet from what I recall, but you have to have something with Medusa on it. Might as well triple dip Alexander and add some bronze to the mix. Another coin that can be had in nice shape for under $100 and most likely $10 - $40.

5. I have to cast a vote for that Rhodes flower reverse. I am not certain, but I seem to recall reading about this coin at some point in history being confused as having Jesus on the obverse despite the coin predating Jesus Christ by 100's of years.