The whole point is that it is not a multiplication with a conversion rate, it's a mapping that is not purely multiplicative, which has coefficients that in some

The whole point is that it is not a multiplication with a conversion rate, it's a mapping that is not purely multiplicative, which has coefficients that in some regions may be significantly different than the exchange rate, that provides round numbers and stickiness to them, and avoids temporal fluctuations - prices in regional markets get adjusted when the ratio gets too far off, not with every change in excahnge rate, in order to reduce the frequency of price change.