That's a quite low cost considering Heaven's tessellation can sink framerate by around 90% at low res and still 70% at 1920 No AA/No AF (53/39% avg)
You can't compare both applications because Unigine is using Tessellation for everything. This is not happend in Metro2033. In a game the performance drop is very high. Because you can't really play with 20/26 in 1650x1050 on a 5850.