I see the Scorpions as a good investment. I'm kind of a numbers guy, so I tend to break things down (my wife hates it when I do it). A stock Yuasa costs about double what a Scorpion does. If we were actually getting the same battery our bikes came with, and could count on them lasting 6 years, a Scorpion would only have to last 3 years to break even. But the many reports have shown the replacement Yuasa's only last 2-3 years. As such, a Scorpion only needs to last 1-1.5 years to break even. If my new Scorpion lasts 2 full seasons, it will have saved me money; any additional time is free, saving me money. I have little doubt the Scorpion will last 3 years, which comes out to half the cost/year of a replacement Yuasa.
I also take into account my bike is getting a LOT more use now that I own it. That is actually good for the battery (batteries don't like not being used), but also means my bike will have at least 125k miles when this Scorpion wears out; possibly even more than that.