It is super expensive here, cost of a roof over my head increased 9x
But the weather is so gorgeous is kind of cancels it out, basically we don't do pay for holidays as this place is one long holiday, nearly always sunny, rarely particularly cold so we turn the "problem" of no spare money into spending a lot of times outdoors, lots of low-cost hobbies be it cycling or walking. We don't dine out, few takeaways due to needing to be economical, so its the likes of barbeque and sit in the garden. I have an orange tree and eat an orange a day and never get ill so probably the lifestyle is healthy. Most Californians look atypical for average USA being generally healthier. So likely the high cost of living is giving us more life.
Never been to Merthyr Tydfil, nearest I been there is Bristol and Leominster (which is not Wales but England). I have been into the nation of Wales in the north across the top to go to Anglesey to Ireland. If I were in your part of the world, probably mountain hiking would be my thing.
It's a puzzle to live in other high cost cities, like London without the California weather, but I reckon good people find something they enjoy wherever they land.