Around here, it's not worth buying a used splitter, they're just priced too close to new. It's like Honda 2000w generators. I'm not paying $950 for a used one, when they're $1200 new.
Not worth building one, either. I priced that out a couple years back, and was up to the cost of a new splitter, just in hydraulics and the motor. That was before adding steel, wheels, or picking up a tape measure and soapstone. I was hoping to build a 240v electric powered splitter, as I only split here at home near the shop, and I REALLY didn't want to deal with maintaining another gas engine, but the cost just wasn't worth it.
If you're not in a hurry for a splitter, maybe keep your eyes open and see if a fantastic deal comes around, or if someone you know is letting one go. I'd pay $950 for a used splitter if I know it's been maintained and cared for. There's a Champion 34T nearish by going for $1200, new they're $2000, has one season of use on it. If I needed a splitter, I'd probably roll the dice on that one.
Y'all will laugh at me for this, but a few years back I bought a 5 ton electric splitter. I was skeptical, but as I said, I REALLY didn't want to deal with another gas engine, and was willing to roll the dice on $350 to try it. It split 7+ cords, and only failed to split less than 10 pieces of wood. Very nice to put in ear buds and split wood while listening to an audiobook or podcast. Also nice to be splitting wood inside the shop, while rain is being blown sideways outside. No, it's not going to handle a 4 foot round, but I try to avoid that stuff if possible too.
I also have plenty of saws, and ready access to a buddy's 37 ton splitter, any time I want it. That seems to be the best set up. Don't have a splitter yourself, have a buddy with a splitter.