Yes and no. You can buy HitFilm Pro (almost same as Vegas Effect) and Imerge Pro (same as Vegas Image) separately. And if you already own a license for a good image editor (like Photoshop or Affinity Photo) it is unlikely you would need Imerge Pro/Vegas Image, so you should be fine by buying HitFilm Pro.
I mention HOS because it offers a tool to send an image from the Vegas timeline to a pre-defined image editor. I've defined Affinity Photo. So if I send an image from Vegas Pro via HOS to Affinity Photo, it will be added as a Take in Vegas Pro automatically in the end. Nice workflow.