because factors like social relationships or mental health, for example, are not always "purchasable" directly with money

Yes, it isn't purchasable, but if the business economy was geared toward wellbeing, the conditions of society would align to cater for the other factors. The "money" part of it has an impact on the rest of it too. Just like money is only good up to a point, not enough money will have negative impacts on the parts of life that can't be bought also.

The monetary economy doesn't live in a vacuum, it interacts with all other parts of our lives also.