The biggest problem with advice like what percentage of income to spend on (e.g.) housing is that these expenses aren't linear with your income.

If you make $50k gross, and let's say $40k net, you may need to spend more than 30% of your net ($12k/year or $1000/month) on housing, especially in expensive areas.

On the other hand, if you make $500k gross, and let's say $300k net, you don't need to spend 30% of that ($90k/year or $7500/month) to find a lovely place to live. In fact, you may be able to "make do" with 15% of net.