In Elder Scrolls 5: Skyrim, septims are small, golden tokens used as the primary currency in the homeland of the Nords, alongside all of Tamriel. As they aren't hard to come by, however, septims inherently become less valuable to the Dragonborn as time goes on. Since this gold-coin trope has been used throughout much of fiction, it can be hard to determine exactly how much the Skyrim septim would be worth to the real-life player.
With not much yet revealed about TES 6, Skyrim's sequel could diverge away from the stereotypical gold coin and give players a breath of fresh air. But if the rumors are true, the game could be set in Hammerfell, and this would meaninglessly replace septims with a standard gold coin instead. It's the hope of many fans that several of Skyrim's downfalls are fixed in TES 6, such as cooking - but it's impossible to speculate on something that still remains so vague. Thus, many fans' attention still lies on Skyrim and all of its details: such as calculating the real, declared value of a septim.
Gold Material Would Make Skyrim's Septims Valuable In Real Life
According to this post by Hail the Empire on the Elder Scrolls Wiki, Skyrim's septims are comparable to modern-day gold coins size-wise. With the metal still retaining much of its value in the current economy, the fictional currency certainly wouldn't be as worthless as it eventually becomes during the Elder Scrolls title. Since gold coins are worth approximately $143 (USD), this is likely the same value that the septim would hold today. This is a straightforward, yet logically sound comparison that shows just how rich the Dragonborn really becomes during the events of the game.
In-Game Calculations Make Skyrim's Septims Less Valuable
However, as Hail the Empire explains, it's also possible to calculate the approximate value of Skyrim's deeply historical septims by comparing the price of in-game items to those same items in real life. Four such comparisons are made: cabbages, carrots, horses, and bowls. The conversion for horses was quite off, coming out to a very inexpensive $500 USD, but the other three items remained more or less consistent across the board. When comparing the average prices of real-life cabbages, carrots, and bowls to those same items in Skyrim, the value of a septim could be approximated to that of a quarter, or 25 cents.
Although prices will have fluctuated slightly between Hail the Empire's post in 2017 and present day, the difference between the first calculation and the second are vast. Elder Scrolls 5: Skyrim septims could either be worth $143 USD thanks to their gold composition, or they could be worth roughly 25 cents when considering their value in day-to-day transactions. For a game so full of mystery and nonsensical quests, like Skyrim's Dark Brotherhood initiation, perhaps this ambiguity is ultimately for the best.
Source: Hail the Emperor/Elder Scrolls Wiki, Bethesda Softworks/YouTube