This is a terrible business strategy. You will win more customers and referrals for life by being honest with people. Sounds like you have a good handy man.

Early in our business we had a contract to replace a bunch of ceiling tiles in a car dealership. Because the ceilings were so high the customer really wasn't sure, beyond the obviously broken or stained ones, how many needed to be replaced and which ones could be salvaged. He gave us the ok to replace up to 300 tiles without needing to get another authorization. We purchased 300 tiles with an agreement from the supplier to return any unopened packages we didn't use. During the job we discovered most tiles were in great condition and just needed to a light vacuum to get some dust off and they looked brand new (especially from the ground). We only had to replace 50 or 60 tiles and my business partner wanted to exaggerate and replace about 100 more since we were authorized for 300. I said no. The GM was so pleased at how much money he saved compared to what he thought it would be that he referred us to two other car dealerships nearby and we ended up getting 10's of thousands of dollars worth of work from them because we were honest and saved this guy a couple grand.