Obsession with Money

What to do if a key older relative in 80s (healthy and well) is obsessed (always has been) with talking incessantly only about money (costs, saving yet more money, price of things, electricity, gas, petrol, cleaning products, milk, the benefits of thriftiness etc).
To the exclusion of any other topic?
Despite being more than well-off, high income from pensions, having a well maintained home, cash savings to last ten lifetimes and nothing monetary to worry about. Meanwhile zero interest in world conflict, or their younger family members of different ages - who are all good and kind and sensible and try to be imaginative , - & with infinite patience !
Trying to be joyful around this is getting even harder.
We have also had a family tragedy but this is pretty much glossed over too.
They would not even spend a few pounds on an outing for social pleasure if there was a cost involved.
PS The emoji is meant to be a whine (a whine is allowed sometimes!) but will appear hopefully as a nice glass of wine instead !
Thank you for reading. Unfortunately it really is a serious problem getting family down, as we all thought it might get better one day. It's hard to believe one person can have this impact on everyone else.
We think people will refer to the loneliness issue- and yes this is sadly a problem - but in this instance it's sadly been created by the negative attitude. Other people /neighbours shy away eventually when they realise how tricky it can be. We visit regularly and do our best, always have done, go on outings etc - host birthdays nd so on - but it's having an impact on everyone and there are no real solutions. We try to encourage thinking about local charities and voluntary schemes etc but this doesn't work either.
A local church or community might be able to provide support but this has also been tried to no avail. This has always been a bit like this, so it's not age related and I rather suspect neuro-diversity maybe, although not sure if this is the right take on it either.