[windthrown]

What is your basis for "It’s more costly to handle cash than to pay credit card companies."? It seems much more likely that they are encouraging cash with lower prices to avoid paying the typical ~1-5% transaction costs to Visa/MasterCard/Amex rather than a large scale tax evasion scheme.

I understand your point about handling cash requiring more labor (no self serve, armored trucks, etc) but I'd be surprised if the cash sales were less profitable than credit cards.