I honestly don't think it's a terribly meaningful question, for the reasons mentioned above (e.g. it's a pre-industrial economy), and for others. Firstly, if this is not a later medieval campaign, it's not a cash economy. Most currency is in labour (even nobles don't have large amounts of coin). Also, the home ownership rate is far, far lower - the vast majority of people are tenant farmers, and by tenant, that means they provide their labour, not money, in return for "their" land (which actually belongs to the Lord of the Manor). But even the Lord of the Manor isn't awash with cash; his land is owned by the King, and he gets most of his "income" in the form of labour.
I realise that a D&D style world doesn't usually mirror this very closely, but it's still worth considering, because the medieval mindset wasn't similar to that of today, where we go out to work in order to earn money, and then we use that to pay for our food, accommodation and then luxury goods and services. It's not even close to the same world, so to say that 1 copper piece equals a dollar, isn't, I don't think, a very useful comparison. We can say it of course, but what does it actually mean?
If your campaign really is "modern people in jerkins" then sure, $1 = 1cp (or whatever). But...