I don't think the ratings are exactly honest. They are calculated using max rating of pump and cylinders and you certainly would never run it that high without risking personal injury and or equipment failure.
Look at this splitter:
http://www.northerntool.com/shop/tools/product_200326290_200326290
4.5" ram, 3500psi max pump. While yes the pump "could" make that pressure, it's got a relief valve set to somewhere around 2500-3000psi.
4.5" ram has an area of 15.9 sq in.
Now if it truly could do 30 tons that means 60000lbs. 60000/15.9 is 3773 psi. That is 273 psi over the MAX of the pump and probably closer to 1000psi over the relief valve.
Realistically that splitter is around 24 tons.
For 30 tons at 3000psi you would need a 5" cylinder.
My Dad has a homebuilt splitter we used for years and years. I don't know the exact specs, but it used a cylinder off an old bulldozer. I want to say 5 or 6". It happened to have a pressure gauge on the valve body. Typically it would barely even read pressure while splitting. The big knarly stuff maybe it would hit 1000psi.
If that was a 5" cylinder that's only about 10 tons.
I know when I first saw the small electric splitters I laughed and figured it was built for "city folk" that split a truck load of wood a year. I still ended up buying one though. I couldn't afford a big gas splitter, plus I didn't want to store something that big either. I figured if it sucked, I would just return it.
In the last ~3 years it has split at least 15 cords, probably closer to 20.
I'm sure it's not as fast and of course not as powerful as a gas splitter, but for $300 something that can split 99% of the wood I cut, I'm happy with it.