testing is an expensive process - this is not true if we give more priority to early testing then automatically we do not have to bare more cost on maintenance or correction.
finding bug is the only task of tester - it is true that finding bug is the major task but along with that they are also domain experts of the particular software, they could help the business analyst as well as the developer, developer is responsible for only few modules but as a tester, they have to see from the large prospective,testers understand the overall workings of the software, what all dependencies are and how one impacts to other module.
Testing is a time consuming process- at the time of sdlc testing is never a time consuming process , the best answer is early testing.
Test Automation can be used wherever it is possible for large projects - no its not true until or unless our requirements are not freeze.
Complete Testing is Possible - for some aspect it seems true but complete testing is never possible. it might be possible for some scenarios that they are never executed by the test team or the client during the software development life cycle and may be executed once the project has been deployed.