Upvote:0
One way to convert ancient currencies is to find out how much of a given item it can purchase (steel for example) vs. what it can buy in a per mass equivalent today. Steel 1000 years ago was a handmade, very expensive material to acquire. Today thanks to furnaces, steel is $0.03 a pound.
from a material standpoint, Given that a sestertius was valued as 2.5 grams and one ounce equals 28 grams, a sestertius would be equal to 0.09 ounces. According to Monex.com, silver is worth $31.69 per ounce (on Oct. 24). Therefore, one sestertius at 0.09 oz is worth $2.85
Upvote:2
Value of money is not the same as in Ancient Times. Today, we use fiat currency, and use it for absolutely everything.
At those times, money was a commodity currency and quite scarce; trade by goods was more common than trade by currency. Not to mention that needs were very different (hence the value of those needs was different as well) and products that nowadays are common and cheap could be really expensive at that time, so it's very difficult to do a direct translation of prices.
But if we use the commodity approach just as if we were in Roman Empire and we have that:
From Sestertius
the silver sestertius valued at two and one-half grams. In practice, the coins were usually underweight.
Silver Price per Gram $0.55
then...
2.5*0.55=1.375
which is pretty close to your figures, and somehow logical, because it's a commodity currency.
So now let's go to the values...
Lollia Paullina jewels: 40,000,000*1.375=55,000,000 dollars
Cleopatra's pearl: 10,000,000*1.375=13,750,000 dollars