I am in the same position as RAFbloke except I have some US ratings too. I am about to do the US Commercial flight test having studied and passed the knowledge test for all of £150.
Also having the FAA IR means a reduction in the hours of training required to do the JAA IR but I still have to do the exams. The FAA CPL will achieve the same. All in all I will do the ATPL exams rather than the CPL and IR seperately as I am not that worried about the 36 months.
Someone obviously thinks that cost = commitment which is not right.
I read somewhere that there are something like 41,000 certified flying instructors in the US although only 11,000 are active instructors. What it does mean is that the development path open to pilots makes it easier for them to improve their knowledge and skills and make them better pilots.
My reasons for becoming an instructor include becoming a better pilot and teaching is one of the best ways to learn. You would thing that the powers that be would be wanting to make it easier not harder.