I paid about $300 at Lowes-Depot for my 5 ton. It works fine for me (birch and spruce) with a 10 foot 14ga extension cord.
I haven't used it indoors yet, but I could. I split about seven cords every year over the winter (in the back yard after work each evening) and it is a good choice for me. I am paying about 25 cents per kilowatt hour for electric, works out to $3 or $4 worth of juice per cord split.
Compared to paying $150 to rent a gas powered splitter for two days and having to get all my splitting done right now I prefer the relaxed approach.
If I was doing more than ten cords a year I would probably get all my rounds ready in late August, rent a gas powered splitter, split all the rounds at least once over that two day marathon, finish the gnarlies with the gas powered and then use the electric over the winter months.
I find in comparatively soft wood like birch and spruce (my highest BTU choices) the electric can break open the uglies better than I can, in a typical split cord there are two or three rounds that I get part way open with the electric. If my electric can't finish the split I usually leave my maul on its hook and go straight to sledge and wedges.
Given the price of gas rentals ( and the fact that both of my sons are away at college) the electric is a good choice for me.
FWIW I have popped 24" diameter (16" length) birch rounds with my electric splitter at 20 below no problem. Birch does split a heck of a lot easier than oak; and every species I have ever split splits easier the colder it is.