suggests that the images aren't that bad, only one image is unoptimised, and you'd only shave off a meg from the final size.
Running the topmost image through Compressor.io gives a ~82% file size reduction with no noticeable image quality loss, and converting the next one from a PNG to a JPEG reduces the size by ~77%. I think there is clearly room for improvement here.
I wish all common CMSes just did this automatically. Or do they do it, already? (WordPress, Drupal, etc.)
They've all at least got convenient extensions you can install to auto optimise images, like with EWWW Image Optimizer or Smush Image Optimiser for WordPress.
WordPress does if I recall correctly. Though it's been a few years since I've worked with it.