It is difficult for me to comment on your situation as I don’t know any of your medical history and whether IUI is the most appropriate treatment.  Your wife’s FSH is near the top end of the normal range and the appropriate treatment would depend on other factor such as her age and previous history.  Each Centre has its own treatment policy and I would suggest you go back to see your specialist and ask for an explanation as to why they are advising you to proceed to IVF as it may be other factors than just the FSH level.