credit card everywhere... 90% contactless. use credit card. but matchday no alcohol in the stadium normally (they will not make an exception for the final i think, i will keep you informed). And there are no pubs near stadium. But there will be mobile turkish guys selling beer. thats how we drink near the stadium in Gala stadium. So hold some cash for matchday near stadium. so how much cash?
ok,
1 beer is 40 Turkish Lira at stores at the moment = 2 USD. They may double the price near stadium, those guys.
at pubs, at Besiktas and Kadıkoy, it is depending. Last month i paid 50TRY in a pub at kadıkoy. But in nevizade street (taksim) i paid 100 TRY (it was a BJK-GS game so they increased the price).
So, normally 50-60 TRY in pubs. But since english fans are coming they will increase it. 100 TRY = 5 USD probably, we will see.
Turkey in a deep financial crisis at the moment. terrible things are happening financially, i dont wanna talk about that and depress you. Sunday 2nd round elections. Next week there will be fluctuations ( i can not comment on which way, it is not legal, but you get it :)) ) on Turkish Lira. We will see. It will not affect you on a negative way, probably you will have a cheaper stay :))
So, depending on your beer consumption make your calculations, near stadium. Hold cash only for matchday near stadium.
cheers.