I'm gonna give DaleH and B-Faithful (maybe the last 2 anti-Yamaha people on earth) some ammo, but here it goes.
I cannot, for the life of me see the need to run Ring-Free in a 4-stroke Yamaha, except, Yamaha reccomends it. I have never owned another 4-stroke motor that required additives. After 4 years, I've bought some for my motor. As Megabyte says, SIM has some good prices if you buy case at a time, I think SIM will pay shipping.
Having said that, I have never owned another 4-stroke that was as reliable or quiet as a Yamaha, although admiral's Accord comes very close! BTW, Honda does not require Ring-Free.