Final answer:
The fine for using a neck duster or powder puff on multiple clients varies by state, but it can be more than 100 dollars, as it is a health violation due to the risk of spreading bacteria and infections.
Step-by-step explanation:
The fine for using a neck duster or powder puff on more than one client can vary significantly depending on the state and its specific cosmetology regulations. However, this practice is generally considered unsanitary and a violation of health codes as it may contribute to the spread of bacteria and skin infections. Most states have implemented a fine that could be dollars for such a violation because it poses a risk to public health. It's important for cosmetology professionals to adhere to sanitary practices, which often include using disposable tools or proper sterilization techniques to prevent cross-contamination between clients.