So I visit my only LCS around town today, As always I ask if there is any ancient coins for sale. He has one ancient coin for sale- a Constantine era late roman bronze. VF and seemed very common to my novice eyes. I don't have a picture available but here is what I want to share. If I had absolutely zero knowledge about ancient coins, I probably would've bought it. Notice I haven't told you the price yet. Anyway, I had enough knowledge to know it was an LRB and Constantine or Valentinian era, though I didn't look to closely. I asked the Dealer, what emperor this might be? All he could tell me is that it is late imperial Constantine-style issue and that the price is right for similar examples. It was in a cardboard 2x2, with "Ancient Roman" and "$30" on it After hearing all of that, does that sound like a $30 coin? It doesn't to me, I know that most common LRBs will be in the $5-$15 range. So I just know I'm glad I knew better than to buy it.
Without a picture I couldn't even begin to tell you what an adequate price would be. For example, some Constantine coins might only be worth $5 or $10 in VF condition, but other of his bronzes could be worth $50 or even $100 in the same condition. It all depends on the rarity and collectability demand. Simply put, the price will vary depending on reverse types and mints. Style can also make a price difference. A particularly attractive bust or reverse can always add an extra $5 or $10 to a LRB. Heck, we don't even know if it was a Constantine. Maybe it's a Magnetius, or some usurper. Or a Julian, or a Constantius, or Constantine II, etc. Some of those could be well worth $50 or even more in VF condition depending on reverse type and mint.
I agree, and I plan to delve a bit more into it, maybe take a picture, however my concern still stands on my dealers lack of adequate information regarding the coin.
My unkind side suspects that it could be one of the common fakes with Constantine on one side and a Widow's Mite on the other. $30 is too much for something being sold by someone who knows nothing. For that price, you could get a coin worth owning elsewhere. I suggest you do that.
My local US-coin dealer rarely gets any ancients, even though he evaluates many estate collections. My area of the world is more interested in silver dollars and gold. So, when he sees a few ancients (almost always mediocre late Roman bronze) in a collection he values them at zero. I am the only guy remotely interested in ancients that he knows. So, he can put any price on them and hope a tourist decides to buy. But, he has all the "room" to bargain. If a US dealer puts $30 on an ancient coin and you can demonstrate you know it is a $5 coin, he might well sell it to you for $5.
More likely he will value it high according to ads he has seen and the belief all ancients belong in museums. After he has had it for a few years, he might come down. I never bother with a shop that has a large sign in the window "We Buy Gold". I'll miss a few that way. Few.
In the Bay Area we have some coin shops with what Doug points out - "we buy gold" and then when you go in there are no ancients, just bunches of U.S. coins with some error or other which I guess makes them collectible, but not to me. Some world coins, etc. There are no brick and mortar stores specializing in ancients. The well-known dealer Frank L. Kovacs maintained some inventory at his Post street location in San Francisco but that was a long time ago (pre-Internet and I was 14 years old) and he specialized in mail order auctions.