All legal but very highly suspicious, maybe not in the drug dealing kind of way, but in the tax evasion kind of way. I am not sure what country you are from, but that 100k limit is per bank, so you can easily open different accounts when you exceed that limit, it doesn't have to be in one country. (If you are that concern that multiple banks will crash, buy gold or land, that money of yours will not be worth be paper then) And I think that in most EU countries those 20k cash transactions are not even possible. All of this might not come in people's mind right away, the drug dealing scenario is more likely, but most will definitely find it dodgy, even if it is not.