How to remove the job price and purchase button

If you're trying to showcase services that don't have a price, or need more information before making a price offer, you can use the "Custom" price type.

Sellers can choose this option when posting a job, if it is enabled in Pricing Settings > Job Values. It can also be the only option available, which will turn the whole marketplace into a service listing directory, and all the transactions will be based on custom offers or requests.

The admin option:

The job price field in the post new job page:

The single job listing page:

You may also want to make sure that you have enabled the custom offers feature in Jobster > General Settings > Features. Minimum license required is Webmaster.
It is still going to work otherwise, but missing the custom offer button.