As a tester, being involved early in the development process can mitigate code defects later down the line. More than 50% of code defects originate from faulty requirements. Using prior knowledge and experience, a tester can help identify high risk areas and work with the development team to plan out the approach in the most efficient way. Fixing defects at the design stage is likely to cost up to 30 times more than if identified at the planning stage and up to 100 times more if not identified until the production stage.
Ultimately early tester involvement saves time and money, making the best use of the client's budget, as any potential and predictable issues have been addressed from the start.