> A local hairdressing salon owner/director doesn't earn a lot more
That is linear thinking, however income is very non-linear. In New Zealand minimum wage is ~$800 for 40 hours and you might have $100 disposable income after living expenses. Let’s say the owner gets $1200 at the end of the week. Their disposable income has increased by wayyy more than a 1:1 ratio. That is why you really care about a $0.50 pay rise if you are working near minimum wage, because it makes a huge difference to your marginal disposable income.
If you are “normal” minimum-wage then you compete for rental properties against all other normal people, so costs rise to soak up disposable income. A similar dynamic occurs for most people in middle/professional income levels - people compete against each other to pay as much as possible of their income on their mortgage and so they also don’t end up with as much disposable income as you might think. You probably know people in the 1% income bracket that are struggling to make ends meet due to that reason (they are way better off, and have far more disposable income and savings, but not as much as one might naively assume).