It can buy happiness for people with intact mental health, yes
My husband has a 20 year history of poor mental health. Three years ago, he had a complete and terrifying breakdown. We’re not in the UK so obviously not under NHS.
We have private health insurance so he was admitted to a private mental hospital within 48 hours of seeing his GP (who saw him same-day as we contacted the surgery for an appointment), he spent three months in hospital having every single treatment you can imagine- CBT, one-to-one psychotherapy, psychiatric care, nutritional advice, fitness classes, music therapy etc.
Because he’s lucky to be in well paid and permanent employment with full sick benefits, he was fully paid for the time he was out of work (11 months in total). We’ve always had I come protection insurance so had that as a back-up.
The hospital he was in is in our city and I was able to see him every day. The cost of parking/bus fare/taxis wasn’t something I had to consider.
When visiting, I was able to walk in with stacks of books and magazines and treats that I had no problem buying.
I’m also lucky enough to have a well/paid, permanent job that gave me the flexibility I needed to support him. If I was working on a minimum wage zero-hours contract, I don’t know what I would have done.
He ended up on a lot of medication that we had to pay for out of pocket- we’ve never had to worry about choosing between his medication and our food shopping.
We were able to go on holidays and weekends away as he recovered, and the change of scene helped him immensely.
We were able to keep up private therapy for him.
There’s nothing that could prevent my husband having a mental health problem- it’s just the luck of the draw, like many illnesses. However, having money helped us hugely during such a difficult time. So, while it didn’t make us “happy”, it took away a lot of things that would have made us much, much unhappier.
Similarly, I’m fortunate to never have had terminal cancer. If I did, I’d obviously be devastated at the thoughts of leaving my family, but knowing that I have life assurance, private pensions, investments etc would mean that I’d at least know I was leaving them with financial security and removing that worry.