They were significantly lower during the no-poach agreement. After it ended, Google immediately raised all its engineers' salaries by ~15%, and salaries quickly increased from there.

Look at self driving car engineer salaries today. Those wouldn't have happened under a no-poach agreement. Compare to the mobile OS race, with tens of billions of dollars (at least) on the line. The no-poach agreement between Apple and Google prevented them from beating each other with engineers, so the money poured into lawyers' pockets through litigation instead.