When reading about earlier times, the costs of various items are often mentioned, as are wages for different kinds of work. To get any sense of meaning from these numbers, they need to be compared somehow with equivalent costs in our present currency. But the estimation of inflation is far from an exact science.
Here’s a site that looks at historical vs current costs from multiple angles: Measuring Worth. I haven’t studied it in any detail yet, but it looks interesting.
See also this: Prices and Wages by Decade, 1600s-2000s