Ticket prices for Monday's highly anticipated World Cup Round of 16 clash between the United States and Belgium at Seattle Stadium continued their significant descent in the hours leading up to kickoff.According to ticket-tracking service TicketData.com, the "get-in" price for the match as of 1pm ET had plummeted to $1,508, which represents a 27% drop over the past three days. After reaching $3,115 shortly after the matchup was confirmed on July 1, the get-in price fell as low as $1,283 on Sunday morning.This pattern largely mirrors the broader trend observed across other Round of 16 fixtures. Although England's victory over Mexico in Mexico City on Sunday night commanded a "get-in" price of $3,820, most other matches have experienced notable declines. The average "get-in" price for all Round of 16 games has fallen by 3% in the last three days and 8% over the past week.For instance, the get-in price for Argentina's match against Egypt on Tuesday in Atlanta was $1,599 on July 4 but has dipped to $1,378. Belgium will be looking to send the last remaining co-hosts out of the World Cup (Reuters)Switzerland's match against Colombia in Vancouver on the same day now has the lowest get-in price among the round of 16 games after dropping from $972 to $719 over the past two days.In contrast, Monday's Portugal-Spain game in Dallas saw a more modest dip from $1,367 to $1,311.The considerable price drop for the US-Belgium match is somewhat unexpected, especially given that Belgium's base camp is conveniently located just 10 miles south of Seattle Stadium at the Sounders FC Performance Center. This will be Belgium's third appearance in Seattle, following a 1-1 draw with Egypt in the group stage and a dramatic 3-2 comeback win against Senegal in the Round of 32.The victor of Monday's contest in Seattle will advance to face the winner of the Portugal-Spain match in Los Angeles on Friday.It could be Cristiano Ronaldo’s final World Cup match if Portugal are eliminated, with the iconic forward set to be 45 by the time of the next World Cup in 2030. Ronaldo has scored three goals at this World Cup, including getting his first knockout goal against Croatia in the last-32.