I wrote my initial answer in the middle of the night, so I took more time to do some extra research. Unfortunately, I tried to track back the 90s study but couldn’t find it. However, there doesn’t seem to be a general agreement on the matter. For example, in Ancient Greek Religion by Jon D. Mikalson, the author says this in his preface:
“I throughout offer what would seem proximate equivalents in dollars for the ancient Greek monetary sums, at the rate of one drachma to $100. In fifth-century Athens, one drachma was roughly the average daily wage, and by our conversion a lower -to middle-class Athenian would earn approximately $30,000 a year.”
As you can see, that’s double compared to the proposition made in the 90s, even with the inflation rate. If we accept Mikalson’s idea, this would make an obol worth around $16.
At the other end of the spectrum, M. Vickers and D. Gill, in Artful Crafts. Ancient Greek Silverware and Pottery proposed in 1994 that a drachma would be worth £1,80 (£3,05/$3,90 today with inflation). Here’s the method from a peer-review:
“An Attic pot with two or three figures on it cost about a drachma; bigger ones with up to ten figures are labelled as worth two or three drachmai. A drachma was the average daily wage, something readily intelligible as a value in any period, but this will not do for V. and G. since a pot costing one or more days' wages is hardly cheap for the majority of the population who could not afford silver and gold, however little it might seem to the very rich. They therefore propose a modern equivalent for the drachma/day's wage of £1.80, surprisingly based on monetary values of gold in antiquity and today.”
And we’re talking about a drachma here, so an obol would be worth merely 65 cents. I also found a 1988 article using an old equivalent rate from 1905:
Even if we add up the 2,857.73% of inflation between a dollar today and 1905, we are still very far from having the same result.
This is what I mean when I say it’s very hard to compare. It wildly depends on what factors you use to calculate such a thing.