that we needed a $15,000 new roof, the second guy told us that we needed a $7,500 patch job, and the third guy quoted us $21,000 for a new roof. A friend who was in construction found and patched the leak in under 5 minutes.
In school we were given a study to read that showed that the vast majority of dental procedures were unnecessary.
Charlatans are in every industry, that's why it's a good idea to get second opinion on anything that seems expensive