Definición de feria:
- Mercado que se celebra al aire libre en unas fechas determinadas y en el que se compran y se venden todo tipo de productos, especialmente agrícolas y ganaderos.
- Evento en el cual se paga una cantidad (relativamente) pequeña de dinero a cambio de participar en un sorteo con premios. (a raffle)
Note: sporadically some raffles are free and you can get some money.
Hecho implicito: En las ferias normalmente se encuentran atracciones (games) donde puedes ganar un premio invirtiendo poco dinero.
Contextual meaning: Inferring by the context you may think, "Feria" has a connotation of wining something without much effort, just for fun (as when you go to the attractions in the carnival) or to get money for free which is more likely to be the origin of that contextual meaning for "Feria". It is not just that "Feria" is an interchangeable word for money it also can be conceived as the event which lead people to get money.