Estimated remittances to Mexico in 2022 totaled $58.5 billion and were the largest single source of government incomeNot too sure but I'll go ask some drug dealers here and some cartels in Mexico and see if they are willing to pay taxes.
Estimated cartel profits are all over the map, with the highest number I've seen being $500 billion. How much of that do you think is shared with the Mexican government since they aren't paying taxes only bribes?
Certainly a 10% tax on remittances would be felt by the Mexican government, and $5.85 billion would buy a lot of wall if it was dedicated solely to that purpose