Medium-sized cities usually have a lower cost of living than the countryside

It seems to be the case in Korea and most other countries around the world.
Being in the countryside doesn't necessarily mean the cost of living is cheap.
First of all, transportation itself costs a lot,
you have to buy your own tools and do all your own home repairs,
and neither restaurants nor manufactured goods are any cheaper than in the city.
It's just that land prices are cheap,
so it's for purposes like buying a large plot to farm or living a quiet, leisurely life..
But in reality, it's so inconvenient that many people end up regretting it.
Usually, a medium-sized city located far from the capital seems to have the best cost of living.
In Korea, Gumi is a prime example,
in Japan, Kitakyushu holds that exact position,
and in Thailand, Udon Thani is just like that. For Vietnam, it might be Nha Trang?