It's not wildly unlike a normal highway bridge. That's about what they cost.

Also

Aside from the freeway overpass, the construction continues. Workers are building a second large structure that will bridge a local road and connect the overpass with the surrounding steep hillsides. Once that’s completed over the summer, they will haul in 3m cubic feet of soil – enough to fill half of the SoFi stadium – to bridge the gap between the overpass and the surrounding landscapes. The construction teams will also build berms to block out noise and light, and add wildlife-proof fencing along the freeway.