i. Collect information about your visitors
ii. It's more professional than just an email address link.
iii. Set pre-defined questions to filter different customers groups.
iv. Reduce spam because you don't have to publish your email address
This is a must have in today's website. It not only makes your website look more professional, you can set pre-defined questions for your visitors to answer so that you can have all the important answers before replying, and also helps to reduce spam as you do not have to publish your email address.
There is no recurring cost until you feel that you need to change your questions, and even so, the cost is extremely low, even lesser than eating out at a restaurant.