you're presupposing that your experience of cash transactions is and should be everyone's experience of cash transactions. Yes, many normal people sometimes conduct business with larger amounts of cash over 10k euros, which by the way isn't all that much anymore. And even if this is unusual, banning the unusual is a terrible way to run laws. If you defend financial privacy, I can't see how you could defend such an idiotic and intrusive law.

>Is that a fancy way of saying tax evasion should be legal? Any transaction of that size represents a significant piece of income for someone.

No, it's a way of defending the basic idea that the state's right to squeeze every penny and justify any law in the name of being able to do so shouldn't be automatically unquestioned. You saying that this cash amount represents a significant piece of income for someone takes as given that the cash in question is being laundered or used for evasion. Do you really believe that this should be a default assumption, or that it's right for the government to assume such guilt just because money is present in someone's daily business? Imagine if all legal issues were handled in such a disgusting way. For some reason, too many people put on emotional blinders and with tax law, ignore how barbarically stupid that is if any respect for presumptions of innocence exists.

You are certainly naive about how reliable government is about being able to pry into everything financial, or how absolute should be its right to squeeze for any amount of money.