Does anyone knows how to get a one day ticket discount or where to buy cheaper tickets?

HR and Travel Agents/Reputable travel sites are good options as well as try the hotel you are booking if it's a Hilton or Marriott their Concierge might be able to get you tickets through their connections as often they fight for customers by providing the most conveniences and have group tickets purchaed through their corporate accounts.

Check your HR department at work. Sometimes they have a corporate discounted rate tickets. Or check your airlines or travel agent. I would stay away from the online non official sites offering discounts. Some are happy to take your money and tickets never come our they are counterfeit.