We can provide the images/assets used on the site for you in a zip file free of charge.
For the site's page content, the CMS's data hierarchy depends on the SiteWrench templates to assemble the pages, so there's not really a way to export page data from the database in a manner that would be useable.
The best option for exporting your page content is for us to crawl all of the published pages of your site in order to generate a static HTML version. This will create a functional, static copy of the content of your site as it existed at the time it was crawled that you can load locally or host elsewhere. It won't be perfect, but will give you a backup of your site that you can refer to and retrieve old content from - similar to what you would see if you loaded your site from The Wayback Machine.
For most sites we will charge for two hours of work at our standard dev rate ($155/hr) in order to cover the time it takes to setup the export, testing the export and uploading the zipped content some place you can download it.
If you would prefer to do the work yourself, it's not very difficult. We use a Mac app called SiteSucker to create these exports. There are several PC options available too, like Cyotek WebCopy. (This is not an endorsement or guarantee of success for either product, but rather is intended to be a merely helpful bit of information).
While this options works well for around 90% of normal page content, there are sometimes cases where a page has content that depends on loading data from our APIs when the page is loaded or uses custom functionality that is dependent on SiteWrench being available. Unfortunately these are inherent limitations that can't be worked around.
If there is important content that you would like to be sure is included in your static export, please ask us about it ahead of time so we can confirm that it will be available or work with you to figure out a custom solution.