Have you tried thinking about things from a cost/benefit perspective? It's still somewhat arbitrary because you only have a rough idea of your utility function

Have you tried thinking about things from a cost/benefit perspective? It's still somewhat arbitrary because you only have a rough idea of your utility function and you aren't going to run all the numbers, but it's a good framework (it also totally justifies progressive taxation because network effects of public goods and services are likely much higher if you have higher income)