If tiles did not require tax, your ore would be completely worthless, because every tile would be mined.
The taxes actually help miners by encouraging non-miners to pay for ore instead of mining it themselves.
I own a single tile that isn't super high value (23 L/h chromite, 400 L/h coal), and It's currently making around 3 mil profit/wk after taxes for a few hours work.
If you're not getting similar return-on-investment, you might want to look closer at your operation instead of blaming everything on taxes.