All four examples have a cutting edge with a width less than 200nm, although the final bevel angle varies from 21 degrees for the Blue Blade to more than 40 degrees for the Olfa blade. The Olfa blade also has a small burr on the edge which reduces the effective keenness.
At minimum, these examples demonstrate the scale at which we need to resolve and image features is well under one micron.
With our definitions of Keen and Sharp we can see that all blades have similar keenness, but the razor blades are sharper than the scalpel and utility blades. The images below demonstrate that the Feather Super Pro Artist Club blade is much keener than other manufactured blades, but is not nearly as sharp as a conventional straight razor.