Each government in ancient times declared its own money of account, as well as weights and measures. At the same time, they all used common words. So, there's an Assyrian mina (frequently translated "pound," whether referring to weight or money), a Babylonian mina, a Greek mina, an Egyptian, and so on. Many units of weight and measure had both a large (royal) and a small (common) definition. This all sounds ridiculous until you realize we do it, too: a "ton" can mean a "short ton" of 2,000 lb. or a "long ton" of 2,240 lb., while a metric "tonne" is something else again.
Anyway, it brings to mind the old question of what a "talent" is. The common talent of silver -- the one most commonly referred to when reckoning in money -- was 60 minas. The mina started out at 60 shekels, but by Jesus' day was set at 50 shekels. The earlier shekel was worth about 3.5 denarii in Roman money, but later on came to be defined as 4 denarii.
So, if a talent = 60 minas, and a mina = 50 shekels and a shekel = 4 denarii, then a talent = 1200 denarii. A denarius was the common "day's wage" in New Testament times. The average daily wage in the US these days is $70. That would make a "talent" more or less equivalent in buying power to $84,000 today. The servant given 5 talents to invest had approx. $420,000 at his command.
Of course, given the actual weight of the silver involved, if you're figuring actual metal and not "buying power," well that's a different kettle of fish. The typical shekel of ancient times had about 11g of silver in it, about .35 troy oz. That would make a talent 330g of silver, or 105 troy oz. Today's silver price is $18.64 per oz., which would make an actual talent (by weight) of silver worth only $1,957.20. But that's inflation for ya.
They had that back then, too. As the prophet says, "he who earns wages earns wages to put them into a bag with holes." (Haggai 1:6b)