For example, if you go to Ritchie Street in Chennai, India there are plenty of stores that will sell you a top of the line GTX 1080 GPU for cash. No record of the transaction, and no taxes. A lot of stores will probably even accept USD.
You wouldn't be able to launder boatloads of cash this way, but with enough motivation you could do this on a regular basis and offset some cash.
This is a very profound loss of individual freedom, almost as important as losing right to free speech would be, yet strictly no one on the political spectrum seems the least concerned about it.
Be careful equating money with free speech.
Citizens United in the US has had equally-troublesome consequences, based on the premises that corporations are people and money is their speech.
Conflict of interest plays a role here, and that's unfortunately something that has been under constant 'redefinition', especially in the last 20-40 years.
Taxes are 5-18% on top of that.