Just thought I'd share a "cute" story about RNG, slightly on topic due to Reika's response.

Once, out guild lead successfully 5x melded Strength onto some +1 gloves. It was crazy... all T IV materia. No matter how much we offered the person that commissioned refused to sell and rightfully so. They were pretty epic handwear. We all still remember to this day; and are super jealous.

Where as another friend of mine had gone for a triple IV Int meld on a hat at least 30 times, and has yet to succeed.