With statements like that you just successfully banned yourself from ever being adopted by real life merchants ever. Merchants can already escape the VAT via cash yet most don't do this - why? Because the risk of dong so is in no relation to the reward of doing so. No merchant in their right mind would ever accept a coin whose customer would annoy him with the request of "selling them the stuff under the table" especially if accepting the coin would basically guarantee him he instant attention of the tax authorities.