We'll, just like you said, it is dependent on the country in which one is located. A US citizen might need more than 1btc at its current price to secure his future, however when you convert 1btc in dollars to other currencies especially African currencies, you'd realize it's a whole lot of money and it's enough to secure one's future
1btc is currently $33000
1btc in South African Rand is 502,000
1btc in Egyptian Pound is 520,000
1btc in Ghanaian Cedi is 193,000
1btc in Nigerian Naira is 12,000,000
These are huge amounts of money in these countries and are enough to set one up for life.
It doesn't make any difference. A Big Mac-Meal which costs $5.99 in the United States will cost 2,300 Naira in Nigeria. So you can't really say that when the exchange rate of the national currency is low, the cost of living will automatically will be lower. In some cases, it may be the other way around. Especially if the national currency is prone to inflation and volatility.
BTW, the following is the price of an iphone 12 pro (128 GB version):
USA: $999
South Africa: ZAR 29,000
Egypt: EGP 22,222
Ghana: GHS 11,309
Nigeria: NGN 620,800