The cost of First is definitely a little more than $100 premium over coach. Usually you can configure more than 2 times the number of seats in intnl coach as in intnl F. Airlines find F expensive enough that they reconfigure it into J or Coach when the yields are low. Many don't even offer F and instead settle for J or premium J.

I personally feel that the best value of miles/points is international premium travel (F in particular). Taking your spouse/SO in intnl F if you are into that sort of thing is made so much easier by miles. RTWs and discounts do cheapen the value of miles redeemed in F or J.