MIAMI—It's no surprise that trophy office space is the by far the most expensive to lease. Would you believe that trophy office space sees rental rates 77% higher than other office buildings? That's according to JLL's 2015 Digital Skyline.

Specifically, average trophy rates in the first quarter of 2015 were $57.97 per square foot compared to $32.70 per square foot in non-trophy buildings. JLL reports this gap between represents a seismic shift from historical spreads: 10 years ago, the difference was just 20.8%.

“International capital is making a long-term impression on the US skyline,” says Steve Collins, international director with JLL's Capital Markets. “We predict foreign buyers to invest $50 billion into US commercial real estate in 2015, and they appear to be buying for the duration. This will have a major impact on future skyline liquidity, particularly for trophy assets in primary markets, where more than half of foreign capital is being invested.”