If a shop charges $80 you can wipe your *** with the results. Cheap sonic testers are as good as experience, internet myths, and machinist’s eyes. A good certified tester, and as important a good human doing it is critical if you want a true result.
Let me ask: you got cheap pistons. You have to buy a crank, and all the other stuff, plus have it machined. How is it too expensive to spend hundreds to determine if the expense of thousands will bring success?