That's right: plural
In Continental Europe, the plural of Euro is still Euro rather than Euros. Analogously, few would claim to have lots of Yens (Japan), Yuans (China), Wons (Korea), etc.
Jay-Z is aware of this fact (unlike most rappers as is evident from a quick search of RapGenius). He emphasizes that his use of Euros is not a grammatical faux pas, but rather an expression of the huge amount of “Euros” he actually sees.
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