As an Arizona WordPress Designer, I often run into situations where a site can be optimized in HTML, but if we are doing an ongoing SEO campaign, the cost benefit of running on a WordPress core increases dramatically. WordPressing a site is not hard, and can often be done as part of a website redesign.
The original design elements were left over from another website designer. I simply cleaned it up, big time. I replaced the bulky javascript that was running the slider menu with nice clean Jquery, I redid the table layout as clean CSS, I proportioned everything. I also put the site onto a WordPress platform, which was a great move. Since we also do the SEO for Veritas Associates LLC, creating a super SEO friendly web design like this was a good move. It paid off well, just search Google for an Arizona Private Investigator, he has been top 5 for a year, #3 right now and closing in on that #1 spot.