don't know where you live but having been on multiple european countries that's not really the case, although many have a minimum purchase amount for paying with cc.
Also if they're giving you a discount when paying with cash its mostly because they're probably not going to register that sale and pay the corresponding tax..
In what European countries do they avoid paying sales tax? Thats Europe, they dont condone such practices. Maybe you are from a third world country where avoiding taxes is rampant because your government is very inefficient in collecting them.
It is a known fact that the consumers themselves pay for the credit card fees. So I dont know what planet you're from.