From glassdoor.com

Software Engineer 697 Google Salaries Average $98,813 Range $70k-$129k

Senior Software Engineer 77 Google Salaries - Average $124,393 Range $63k - $150k

Software Engineer III 55 Google Salaries - Average $103,125 Range: $93k- $115k

Software Engineer In Test 55 Google Salaries - Average: $85,078 Range: $62k- $104k

Software Engineer II 20 Google Salaries - Average: $87,20 Range: $72k- $105k

(so yeah $150k is highest end of Senior SW Engineer)