So you'd give 3 gold coins for a load of bread? Smart.
You have also have to remember, gold does absolutely nothing by itself. You can't eat it, and in medieval societies, there were no real machines that made any use of it. So why do people want gold? Old world economists thought that everything must have an inherent value, and that a value or price of something should be related to how useful it was. Lumber, then should be more valuable than gold, and they couldn't explain why it wasn't. So what's the deal then? If you were to write down a list of all the things you value, there would certainly be things you would value more than others yes? If you compared it to lists other people have made, you'd find that you probably don't value things the exact same as someone else due to each person's individuality. I love pistachio ice cream for example, even more than chocolate. I'm going to go out on a limb here, and say that you probably like chocolate more than pistachio, because pistachio is not a very popular flavor. If you have pistachio and I have chocolate, we would therefore trade, which is the whole basis of economics: human values, which are the basis of supply and demand. Hence why....
This is probably really inaccurate, but at least a shot at it.
A bread is about 2USD in the US, and about 3 septims in The Empire. 1 USD = 1,5 Septims? It becomes more accurate the more wares you compare. But this got me thinking: Magical sword made of the blood of a god that steals you sword for 5,000 USD? I have a strange feeling the in-game monetary system is somewhat simplified... That also makes the USD-Septim comparison hard. (And keep in mind that most people in Tamriel are not poor, but not rich either.
Edit: The sword steals your soul, not sword...
...this would never work. A market in a fantasy game is going to have different supplies of things (bread may be more in abundance for example) and different demands based on human values in order for this to work. You would be better figuring out how much WE (in the real world) would trade for some of these items, and figure out the exchange rates from there. A soul stealing sword for example, is not in high quantity in our world for example. However, it's possible we have more food items and perhaps other things such as cars, etc., that the denizens of Tamriel would love to get their hands out. I would start there and kind of try and guess what the exchange may end up being from that sort of thing.
Which leads me to mediums of exchange. If a chicken farmer mainly has chickens, then he is going to have to find someone who wants chickens to get what he wants, like say....gasoline. You can see where that would be difficult. This is why societies as a whole start to use things that many people value and want or everyone generally agrees is valuable as a medium of exchange. The native americans used beads, and Romans originally used cattle, hence their word for money, pecunia, being similar to their word for cattle pecu. Everyone agrees gold is valuable, and knows that someone else will accept it somewhere.
So what exactly is the problem with spending 3 septims on a loaf of bread? Hm?