Uh??
Why the upcharge for a 4-post?? IMO no harder, and possibly easier/less technical than a 2 post.
#1 the 4 post does not require drilling the concrete and setting anchors, CAN use anchors if you want, but not required..
#2 No, or very little measuring to determine placement on the floor, which can be a bit tricky, and a real bummer if you measure, drill and set anchors and then realize you did it wrong.
4-post lift assembly and install is really not very difficult. There is a bit of lifting requiring an engine hoist and/or 2 people, but the actually assemobly is not technical at all. If you can put together an entertainment center for your TV, you can most certainly assemble a 4-post lift.
I paid to have mine done, primarily for the convenience of having someone else take care of pickup and delivery, which is just a pain. I certainly could have done the assembly, although it would have taken me a bit more time.