i was wondering, in developing countries currency rates of foreign currencies keep changing with the country’s economy and the GDP. but usually the US dollar rate remains the same. i know the main reason behind the stable dollar rate is trade. but why are some currencies are very high priced even though they are not very developed? or some currencies are very low rated although they are developed? for eg. Rupee is quite devalued. Sri Lanka, India, Pakistan, Thailand are the countries i can think of right now where Rupee is the currency. i was checking Pakistan’s currency rates chart and i read that Kuwait’s Dinar in Pakistani Rupee was very expensive and the Japanese Yen is very cheap. its confusing, what actually depicts currency rates?

PS. I am not a student. i have graduated long ago, i am asking this to clear my economical concepts, it is not some assignment. so a genuine help would be appreciated. thanks