If there was separate IR writtens for SEP, MEP, High Performance/CPL/ATPL, which do you think most people would do and what the costs of doing each would be.
Why would you need such a thing? An IR is an IR is an IR...whether it be in a PA28-140, PA34-200T, B200 or a CJ.
Whether you can fly the PA28-140, PA34-200T B200 or a CJ is a completely different matter and independant of the IR.
The IR gound exams will still cost in the region of £800 to complete (compared to $90 and a copy of the ASA manuals for the FAA).