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You are thinking small it's not about just local people football is global.
Revenue is not limited to just people on match day. (This outside of tv money is revenue wise important and it doesn't need to just be local fans having space for tourists is a good thing )
Take a look at the worlds biggest clubs they are global brands this attracts not only people who want to attend games but it increases revenue from sponsors also means they get more exposure tv wise.
Merchandise sales do make a difference if you are not only selling it from just your club shop.
This was a long time ago but when Real Madrid signed Beckham people questioned the transfer fee it was high but the club sold that many shirts it covered that fee.