Yes the sweet spot is about 2.5" of actual lift in terms of cost and function.
Even that's a little complicated though because the advertised lift height might not be the actual lift height.
It depends on the company that makes the kit, as well as how heavy your vehicle is.
A kit from one company on a lightly loaded without heavy steel bumpers might give you 3.5", and the same kit on a heavy jeep might be 1.5".
The main thing to evaluate when you're looking at a body lift is what size tires do you want to run.
The spring/spacer lift only increases the distance from the body to the tires.
The tires determine how high the axle is from the ground.
So unless you plan on running 37's or bigger, a lift larger than 2.5 - 3 inches of actual lift is unnecessary and very costly in terms of all the parts you need to do it right.
As you lift the body of the Jeep, the body of the Jeep moves towards the passenger side and is no longer centered over the axle. The front and rear axles move inward getting closer to each other as you lift as well.
The higher the lift, the more pronounced that is, and the more problems/cost you have on your hands.
The most noticeable issue is severely affected steering response that makes the Jeep feel flighty and difficult to control at high speeds, which is not a great feeling if you've ever driven a Jeep that was lifted over 3" or so with a cheap kit.
With 2.5" of lift, you can get away with needing to replace things like the control arms, drive shaft, drag link flipping and a host of other changes/parts that would be needed.
A 2.5" lift can fit up to a 35" tire if you get some aftermarket flat fenders so it's a great compromise in terms of performance and cost.
