These are microscopic objectives. there are many other more popular options that are commonly used by microphotography users such as the Leitz Photars and Zeiss Luminars and some of the newer Apo super long working distance objectives. Selected Photars or Zeiss can be even more inflated in price, and are probably due to them being collector items.
Most of the time they do stacking to achieve the dof.. diffraction easily hit the moment u increase the aperture slightly. For much larger magnifications, u might end up with hundreds of stacks that are taken adjusted by micrometer apart. Because of the extremely short working distance, illumination can be an issue.
Adapter is not easy to get. My previous RMS to F mount adapter cost me a bomb online ( somemore it is plasticky and fragile looking ... )