If we think about 50.000 euros, it means 100 banknotes in denomination of of 500 euros. And yes, this amount should be declared when leaving the country. But if we only think about how to carry this amount, it's not too difficult to carry 100 banknotes, is it? They can easily fit inside a pocket.

However, since I understood that OP wants to have the entire operation done off the radar I suggested him to make multiple trips to the point of exchanging the money and only cash out amounts of 9999 euros, which do not have to be declared. Alternatively, OP could also plan a nice vacation and exchange more than 9999 euros and spend the money before returning home or return with an amount not greater than 9999 euros.