I took this RR double litra, 275 B.C., Crawford 16/1a for 7€ at a no reserve auction. It needed some cleaning, but now it is quite a decent coin
2020 was way too lucky for me in terms of cheap coins. When I started, in October, I was under the impression that you can only buy some 4th century Roman coins, in poor condition, spending this sum (<20$) I was very wrong. All these coins, plus other, were from a lot of 34 coins I got from an auction with 100 EUR + taxes + shipping. So about 135 EUR, roughly 165 $ , so about 5%/coin. From the 34 coins, only 2 are in a bad state, but they were attributed without problems, both of them fallen horsemen. The rest are good, and even these ones are quite ok, not spectacular, of course, but it looks like I lack all the possible skills at taking pics, they are better in hand. I was under the impression this is the actual price for a Titus sestertius in this condition, 5$. Oh well... Other bargains: Yes, not the best quality but I don't think you can ask more for 10 EUR + taxes 14 EUR + taxes 10 EUR + taxes (the white spots are not present on the coin, this is how the house took the pics) And some MANY other.
For my best ancient of 2020 that cost under 20 bucks, I reckon it would have to be be this one. @happy_collector has it now. I had $18.85 in it, all told. Greece (Mysia, Pergamon): bronze Æ15, ca. 2nd-1st centuries BC; Asklepios / Serpent staff Obverse: head of Asclepius right. (aka Asklepios, Aesculapius, etc.- spellings vary). Reverse: serpent-entwined staff (i.e., Rod of Asclepius). Mysia, Pergamon. Æ 15 mm, 3.2 g. Ca. 2nd-1st centuries BC. Ref. SNG Copenhagen-401 or similar.* Ex-Biga Numismatiek, Netherlands (formerly Alibaba Coins), 13 May 2020.
This neat little (well, not so little, actually) Numidian bronze doesn't quite make the <$20 threshold, as it cost me $20.30. Numidia: bronze Æ26 of Micipsa, ca. 188-148 BC; head of Masinissa, horse Obverse: head of Masinissa (father of Micipsa and first king of Numidia). Reverse: rearing horse left. Ca. 188-148 BC. 13.24 g. Ex-David Connors, May 2020. That was my first (and to date, only) Numidian coin.
This addition was inspired by the wonderful educational site of @Valentinian and even with its wear it is quite a catch for 11EUR: ARCADIUS (383-408) AE3 17mm 2.23g reduced centenionalis, minted at Constantinople, ca. January-February 383. DN ARCADIVS PF AVG; pearl-diademed, draped cuirassed small bust r. CONCOR - DIA AVGGG; Constantinople seated front, head right, holding globe in her left hand, and partly-seen reversed spear with her right hand, right leg bare, with foot on prow; palm branch in left field, HN in ligature in right field. CONSΓ in exergue RIC IX Constantinople 57f, R3 But why? The type was introduced around 379/80 together with its sister "Western" type (Roma seated front) and seems to have been in issue at different mints throughout the whole period between sometime at the beginning of Theodosius reign and very soon after the elevation of Arcadius. The rarity of this type for Arcadius shows that it was soon discontinued, perhaps as early as the end of January or February 383. As the output for the other rulers from this issue is rather scarce, it is likely that this was a brief emission, starting around the end of 382 and ending in early 383, when Theodosius introduced his own "dynastic" types, marking a de facto independence from the West. Two other specs in NDB here, and here.