The question then is how do you assess value for money before you use the service. I work as a freelance tester and I often see that customers see the value aft

The question then is how do you assess value for money before you use the service. I work as a freelance tester and I often see that customers see the value after working with me and then return for repeat business (as someone else has mentioned - you build a reputation). As an example, an error in an iPad app was dismissed as a known connection issue by the dev team because there were no server side logs so the request wasn't hitting the server. This was the dev team's first iOS app. My specialist knowledge of mobile testing helped identify quickly that the app was connecting to the servers but that this one request wasn't and provide console logs showing where the communication error was occurring. This customer were to launch in public the following week and this would have killed their reputation due to the critical nature of the function that was failing. This was my first day testing with them after they had put in a year of development effort and dev testing (they brought me in specifically because they felt they were getting "tunnel vision"). This was one bug masking behind another which I spotted due to 3 years experience in testing mobile apps. I think that provides value for money without being employed permanently, however I appreciate that companies/teams don't see that value until it's their reputation that has been protected by the investment.